Colecovision

ADAMEm - http://www.komkon.org/~dekogel/adamem.html
Open source emulator for AcornOS and DOS.

ColEm - http://fms.komkon.org/ColEm/
A freeware emulator for DOS and Windows by Marat Fayzullin. Older source code for Unix/X is also available.

ColEm for OS/2 - http://home.houston.rr.com/spiceware/colem.html
ColEm port for OS/2.

ColemPSX and ColemPS2 - http://www.geocities.com/james7780/
ColEm port for PlayStation and PlayStation2.

Mission - http://www.komkon.org/~dekogel/mission.html
Freeware emulator for MSX-DOS.

Mugrat - http://www.bannister.org/software/mugrat.htm
An emulator for MacOS X by Richard Bannister.

The Virtual ColecoVision Homepage - http://www.classicgaming.com/vcoleco/
Freeware emulator for Win32 and the Java Virtual Machine. Sources for the Java version are available.