Simple CPU Emulator Links
The source code of the SIDE - Space Invaders Didactic Emulator
A four bit demo computer in Java (slightly buggy, as I discovered)
I might integrate this architecture though...
OpCode Scheme for the Intel 8080 processor
A german Space Invaders Homepage, with a flash version of the game

(GPL Copyleft) Martti Kühne, 20.8.2008