I used a RadioShack project box (6" x 3" x 2"), 3 normally open .5" momentary pushbuttons, 2 Dsub-9 jacks, and an iPAC VE to make a little box that lets me use joysticks designed to work with the Atari 2600.
I've had an Atari jack on the inside of my cabinet for a long time so that I can play some 2-player games from one side of my cocktail cab.
I built this one the other day so I could use my Wico Command and Conquer stick with MAME on my various USB computers.
The pictures show how simple it all is. The buttons on the box are players 1 and 2 and coin1. The USB jack is on one end and everything else is on the lid to the box. The standoffs that the iPAC is mounted on are .75" long, and the button contacts had to be bent nearly 90