I almost did this with an old Pac Man arcade cabinet but the people that were going to sell it to my brother bailed out at the last minute and decided to keep the cabinet.
I purchased
arcade buttons from Sparkfun and picked up a
joystick and a
stuffty coin acceptor from Adafruit, if anybody else is interested in doing a similar conversion. You've got a couple of choice for connecting them to a computer.
You can buy all USB stuff and just hook it straight up to a computer. Probably the easiest way to go about it.
If you'd like to do some more custom stuff, you could buy a raspberry pi and make a pi based mame box. I saw one of these at a Maker Faire and they had missile command running on it really well with a rollerball and everything, although the cabinet was made out of cardboard. You can wire everything up to the GPIO pins on the board for quick prototyping.
Alternatively you could get an
Arduino (or a cheap clone of an
arduino), or a
PIC, or your favorite microcontroller, wire up a pretty simple circuit and then have the microcontroller emulate a keyboard. Send the coin insert command as a letter A, button 1 as B, etc, then bind the keys in mame.
You could also use a
PCI GPIO card to interface between a computer and pretty much any device you would ever want to connect to one. Unfortunately this particular one is like $80 and it's out of stock, but I'm sure if you look around you can find another. On second thought it's probably just easier and cheaper to handle everything on an arduino and then connect it to a PC through a serial connection.
I haven't had much of a chance to work on my MAME arcade yet although I'll probably breadboard it over Thanksgiving break and have it working pretty easily. I haven't figured out if I'm just going to solder it all onto some protoboard after that or if I should get some PCBs printed. I'm using a raspberry pi but in hindsight using an arduino emulating a keyboard is probably the easiest way to do it. I went with the raspberry pi because I wanted a tiny embedded computer that will fit inside the controller unit which will dock with the cabinet (when I get around to building the cabinet) and also removable so that you can take it with you and connect it to any old TV. Unfortunately the raspberry pi is pretty low power and won't run every game I want it too. I'm sure I can run Pac Man, Galaga, Dig Dug, and some other games on it, but I probably won't be able to run Smash TV.
Anyway that's just my experience with working on my mame machine. I'd love to restore an old arcade machine but I don't really have the space to keep one at this point in my life.
Oh, and if you're trying to buy old arcade stuff, there's this site:
http://www.paradisearcadeshop.com/en/
