ADAMEm: Open source emulator for AcornOS and DOS.
ColEm: A freeware emulator for DOS and Windows by Marat Fayzullin. Older source code for Unix/X is also available.
ColEm for OS/2: ColEm port for OS/2.
ColemPSX and ColemPS2: ColEm port for PlayStation and PlayStation2.
Mission: Freeware emulator for MSX-DOS.
Mugrat: An emulator for MacOS X by Richard Bannister.
The Virtual ColecoVision Homepage: Freeware emulator for Win32 and the Java Virtual Machine. Sources for the Java version are available.