I bought an old USB Logitech Wingman from the thrift store, opened it up and soldered a normal 9-pin sub-D connector to the direction contacts and a fire button pad.
Now I can use it as an "interface" to connect any old Amiga/Atari/Commodore digital joystick to my PC. I use my Wico bat joystick to play games on WinUAE and in VICE.
You can buy something similar already made called the Stelladaptor.
http://www.stelladaptor.com/My method only cost about $6 for the gamepad and the connector, though.
