Further updates (source code and wiring) now online.
I've moved the version selection from Arduino pin 13 (PB5, ATmega chip pin 19) to Arduino pin 12 (PB4, ATmega chip pin 18) to avoid a conflict with the power-up LED boot flash if using the Arduino bootloader. Also, the player potentiometers on schematic have been turned around so that clockwise = up, anticlockwise = down, as on the original consoles.
http://searle.hostei.com/grant/AVRPong/index.html
My page gives the required Arduino pin numbers to connect to, but I've now got a UNO board so I'll probably add the equivalent wiring and pic for those using a board.
All source is in one file, no additional libraries are needed, so just load up and program 