There are multiple sites on the web offering products to interface existing Sega Genesis/Nintendo/Super Nintendo/Atari style joysticks and gamepads to your PC. These come in a variety of flavors/styles. Some interface to the joystick port, some to the keyboard port, and some to the parallel port. Some require software drivers, some don't. The sites offering such things that I've found are:

DirectPad Pro is a combination software/hardware interface for hooking up various game pads to your computer.  It currently supports Nintendo 64, Sony Playstation (force feedback!), TurboGraFX, Saturn, Genesis, Jaguar, SNES, NES, and Atari VCS controls.  Because the hardware plans are for you to build, the cost is only your time and the cost of the parts. These devices hook up through your parallel port, and should be automatically useable by any DirectX game.

SNESKEY is a freeware software package by Benji York. It is the software interface used to connect a parallel port adapter device to your joystick/gamepad. Benji has circuit diagrams online for building your own interface.  SNESKEY features support for up to 5 SNES/NES controllers (in addition to the normal PC joystick) for up to 6 player action. Other devices are supported as well as NES/SNES. His latest addition is for Playstation controllers!  SNESKEY is no longer under development unfortunately.  Benji last posted an update to Sneskey called Sneskey9x for Windows95.  He's also added support for arcade controllers!  From a message he posted: "Drivers for the other controllers are being added. I haven't had time to add documentation for the custom built arcade controllers. If you're interested, please contact me and I'll tell you about the (very simple) circuit and how to use it with SNESKey. " Benji was kind enough to send it to me, and it looks great :)  Unfortunately he seems to have disappeared at least for now.  In his absence, I'm posting the information he sent me.  Should he resurface and wish it removed I will do so promptly.

Dennis Brown has started a new project to interface Nintendo 64 controllers to a PC, most likely via a parallel port.  He is seeking any information on the Nintendo 64 controllers available, and can be emailed about it here. This page appears to be dead.  See next link.

Stephan Hans (Many projects), Simon Nield, Earle F.P. III (DirectPad), and Benji York (SNESkey) have been collaborating on connecting a Nintendo 64 controller, and it is now a reality.  Stephan has posted the hardware portion of it, along with some test programs, on his Nintendo 64 controller page.  DirectPadPro has been updated to include drivers for the N64 interface now!  Excellent work guys!  Stephan has replaced the Y-adapter previously being sold with a new dual-interface adapter (in other words, instead of two single interfaces and a Y-adapter, now you just need one dual interface).  This requires at least version 5 of DirectPad Pro. Stephan is no longer selling N64 adapters.  Information left up in case he starts again. It's $25.00 for the complete assembled interface, including cable.  For those on a budget, there's a $10.00 adapter KIT, without cable, that is not a complete assembled interface.  For details, visit the link.  Stephan is now also selling a two-controller adapter for $40. Stephan has cracked the sequence needed for rumble pack support now!  Hope for driver support soon now :)

Apparently with Stephan's blessing (in fact, linked off of Stephan's page), the PC-Doctor is also selling N64 interfaces based off of the above circuit.  His pricing matches that of Stephans, and can be purchased online.

Stephan Hans has updated his site to include some information for people who have had problems getting their adapters to work with their parallel ports.  Apparently, not all parallel ports are built the same, and there are some voltage problems.  Electronics being Stephan's bread and butter, he zaps this problem handily :)  Furthermore, he discusses this: "if you press a single button at the gamepad, SNESKey and/or DpadPro shows two ore more buttons pressed at the same time (by the way: that's why you can't calibrate the gamepad in this case with the DpadPro driver in WIN95/98)" He also goes on to discuss solutions.  Yet another save by Stephan - thanks!

Simon Nield, one of the folks who worked on the N64 parallel port adapter with Stephan, has been at work on a USB console adapter interface.  Currently with support for N64 and Playstation pads, he's looking at possibly adding SNES pads next.  Circuit diagrams and construction notes are up on the site now, so those of you with the desire and expertise should take a look :)  There's some thought that it might work for Mac USB ports as well as PC!  He's indicated that there is someone who might be willing to offer pre-made interfaces soon.

Simon Nield also has a page up for his modification of the Playstation/DirectPadPro interface, called the MegaTap.  It allows for 4 (or more?) Playstation pads hooked up at once via LPT port!  His warning, the circuit is not for beginners and he won't be doing email support on it, but it looks good :)

I found an excellent writeup of the N64& Playstation parallel port interfaces on Emulatronia.  It's written in Spanish, but has incredibly detailed graphics and a very easy to follow circuit diagram.  If you've been thinking of building one of these interfaces, even if you don't speak Spanish, you should take a look.  A downloadable English version of the PSX interface writeup is available from their web site here. Thanks to Dennis, we now have an English translation of the N64 writeup!  Thanks Dennis! Also, ^Techie^ has written up a review of the parallel port N64 interface from Stephan and Simon.  He has pictures, an English component list, and a step-by-step guide to building the interface.  Hosted at EmuHQ.

Ultimate Videogame Accessories is selling the Smart Joydapter that allows you to hook up your N64 or PSX controller to your PC.  Details on the product are scarce, but it's $35 per adapter, plus $10 for shipping/handling (what exactly is handling anyway?).  It now supports up to 20 buttons, and has USB capability.  There is no force feedback/rumble pack support.  Anyone ordering one want to comment?  Thanks to Ben for the news!

Nthero sent me an email that he'd found the Smart Joydapter available from the A.I. Trading Co. for $17.00!  The downside is that it's in HongKong, so shipping & handling may eat up the savings from the $45 price from UVA.  Anyone who finds out please let me know?  Thanks for the email Nthero!  The interesting thing I saw on their page was that it is 4 or 6 button joystick compatible, so you will get limited use as compared to building the do-it-yourself interface.

INTV2PC - Division Software has released an interface for hooking up Intellivision controllers to your PC.  It works with the Blue Sky Rangers Intellivision PC emulator, and does not appear to function with other programs or with the Mac version of the emulator.  You must supply your own Intellivision controller.  This looks like a must have if you're an Intellivision fan!

Jafu sells a PSX gamepad adapter for the PC for $17 shipped, and has several good feedback comments on his message board about the quality of his cables.

Imagination Works Computer Technologies is another vendor selling console adapter interfaces.  They sell a bunch of adapters for game console controllers that use either SNESKEY or DirectPadPro.  These include: The IOMAXNES - 2 NES control pads interfaced to the parallel port, complete $23.99 The IOMAX-SNES - 2 SNES control pads interfaced to the parallel port, complete $42.00 The IOMAXN64 - NES-64 two controller interface (controllers not included), $41.99.  Presently out of stock and not for sale but will return. The IOMAXPSX - PSX two controller interface (controllers not included), $26.99 The IOMAXPSXFORCE - PSX two controller interface with force feedback support (controllers not included), $37. The IOMAXXTREMEMOLEX - WOW.  This product allows you to connect up to two Nintendo 64 Controllers and/or 2 Playstation controllers to your computer for use with games and Emulators. This Product supports all FORCE FEEDBACK enabled games that use the Windows Controllers/Input System. This Product gives you a special printer port for your existing printer and an Additional Parallel port for a scanner or another printer.  Presently out of stock.  $100. The PSXN64TOPCUSB - PSX and N64 to USB port (Windows support only).  Allows connecting either a PSX or N64 pad to your USB port.  $42. The PSXTOPCUSB - PSX to USB port (Windows support only).  Allows connecting a PSX pad to your USB port.  $45.  No, I don't know why you'd buy this one instead of the one above. They plan to offer Genesis and Saturn adapters as well, and may customize a setup for you including a custom multi-adapter.  They'll also soon have an emulator support section with config files for you to download.  Too cool. You can email them at their sales or interfaces mailboxes.

SNES Pad Support Site - Chippy has put together a wonderful site dedicated to disseminating information on hooking up SNES controllers to your PC, and also urging various game/emulator authors to add native support for SNES pads.  In his own words, "I have created this site in an effort to raise awareness among people about the SNES game pads they probably already own.  Did you know that with a simple adapter, and software support, you could use this excellent joypad on your PC?"  His site includes how to guides, links, information on what emulators currently support SNES pads, etc.  Definitly worth a visit if you want to use SNES controllers!

Kernel Productions JoyPort for the Macintosh - Kernel Productions has a product called the Joyport that will allow you to connect Atari, Playstation, N64, Sega Genesis, and PC controllers into your Macintosh.  Models exist for the ADB port, and USB port (iMac).  It even supports the N64 Rumblepack and the Sony Playstation Dual Shock controllers!  PC users are already turning green with envy.  The cost is $54.95 including shipping.  Big thanks to Bryan for the tip!

Game Station X has a great section called Controller Data, with a good primer on on Controller Theory (analog, digital, etc), as well as pinouts and details on 7 different console controllers.  A good read if you're interested in the general principles or want to design a hack.

While surfing through the Build Your Own Arcade-Style Controls site (no affiliation, but a good site), I came across some interesting links, including this one:  Ultimate Video Game Accessories sells a product called the Dreamstation that apparently lets you use your PSX controllers in a Dreamcast machine, with the Dreamcast rumble stuff supported.  You can read a review on the Dreamstation here - there are some drawbacks to the Dreamstation so read the review first if you're considering one. Several folks have asked recently if anyone knew of any arcade stick hacks for the Dreamcast, as it has a fairly unique controller.  Now you might consider hacking a PSX pad, and hooking it up via this adapter to your Dreamcast, and... *presto* -- Anyone doing this please let me know how it works!

Magnet Eye passed on to me heads up about another N64 to USB interface called the Adaptoid.  It not only allows you to use your N64 controller on a PC via USB port, it also supports rumble-to-force feedback.  If you've already gotten one, you need to download the latest drivers if you haven't.  From their web site: The latest driver is 1.2.78 (beta) which has a brand new rumble effects engine which greatly improves DirectX force feedback over the previous driver. As with the last driver release, it has support for Win2000, rumble support for multiple adaptoids simultaneously, allows rearranging of the controller button ordering, and has a driver installer/uninstaller. See the readme file for complete details.

Zerofil clued me in to his site, Zerofil's Neo Pad on PC.  This is a write up of how to use a Neo Geo game controller on a PC using an SNES pad as a relay.  Very cool.  Thanks Zerofil!

Axman's adapters Axman sells adapters for PSX and N64 controllers.

Twinshock Ryan sent me an email on this one. It's a two stick 26 button (basically two players) arcade stick console for the Playstation called the TwinShock. Features include Arcade controller design - 2-player compatible - built-in rumble force-feedback feature - Auto reload function - auto fire function (from their web site). Made by Blaze or Fire International.  Picture.  Hook up a PSX to USB convertor and voila, an easy PSX/PC switchable game cabinet. Add a PSX to Dreamcast convertor, and have an easy 3 machine cabinet. These are available at ebworld.com, and I've seen them at video game stores in the mall as well.

NES gamepad to PC Adapter Druin (of the SNK LS30 Rotary Joystick to MAME Interface) posted this message on the message board: I scanned the article in black & white (since some of the pages were dark blue with black text and hard to read in color, you'd think it was an ELEETE bulletin board run by 15 year olds) and I also saved it in low quality JPG so it would be small, but it's still readable as far as I can tell... So this shows the circuit to connect an old 8 bit nintendo joystick to a computer either via the 15pin joystick port, or with the 8 discreet output switches (which they say are for atari hookup, but Keyboard Encoder is a nicer word). If it's used for the discreet outputs, some of the circuit can be omitted for the joystick interface (transistors are surrounding components).

J.U.M.P. - Joystick Unit Multi-Port From their web site: Welcome to the Joystick Unit Multi-Port (JUMP) Interface web site. On this site you can find information on how to build your own flexible multi-port interface to connect up to 5 NES/SNES controllers to a standard PC parallel port!  What sets the JUMP interface apart is that JUMP separates the necessary wiring into an external interface box instead of permanently joining the adapter circuitry and the controller. The NES/SNES joystick cables are modified to use a standard 9-pin connection to connect to the interface box. Since the crossover wiring is handled in the interface, with a few more modifications you can still use your gamepad on your console system and then simply disconnect it and plug it into the JUMP Interface to immediately use it on your PC! What's more, if you've ever been frustrated by the joystick cable being too short,  those same modifications allow you to use a standard 9-pin extension cable (much easier to find than a NES extension cable ) on the JUMP Interface OR even your original console to add as much length to the cord as you want! Information is available on the site for free on building this yourself, or you can also order if you'd prefer not to build your own.

DigitalPuppy's Escape:  SNES Gamepads to PC Parallel Port Here's another external adapter for your SNES controller from DigitalPuppy's Escape.  From their web site: Here I will explain how to make an adapter where you can plug your Super Nintendo gamepads and use on your computers parallel port (lpt.) You will not need to cut or modify the snes gamepads or connectors therefore you will still be able to use the controllers on the original super nintendo console.