Colecovision

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

ColEm
Open source emulator for DOS, Linux, and Windows by Marat Fayzullin.
http://fms.komkon.org/ColEm/

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

ColemPSX and ColemPS2
ColEm port for PlayStation and PlayStation2.
http://jum.pdroms.de/

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

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

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