Genesis

Blades Of Vengeance
Some ROM Images.
http://accumulator.webz.cz/download.htm

Consoles - Megadrive
A table of the latest emulators and their ratings.
http://www.emulatronia.com/consolas/md.htm

DCGen
A Dreamcast port of Generator.
http://sourceforge.net/projects/dcgen/

FreeRoms: Genesis
Alphabetic sorted ROM list with rating system. (607+ ROMs)
http://www.freeroms.com/genesis.htm

Gametown
Offers a few ROMs.
http://www.familydomain.com/gametown/sega.html

Genecyst
Freeware emulator for DOS.
http://bloodlust.zophar.net/gen/genecyst.html

Generator
Open source emulator for AmigaOS, DOS, Linux, MacOS and Win32.
http://www.squish.net/generator/

Genital
A freeware emulator for DOS.
http://www.trzy.org/

Gens
An open source emulator for BeOS, Linux, and Windows. Multilanguage and Sega CD support.
http://gens.consolemul.com/

Megasis
Freeware emulator for Windows.
http://www.geocities.co.jp/Playtown-Spade/3163/

PGEN
An open source emulator for PlayStation2 based on Generator.
http://pgen.gamebase.ca/

PicoDrive
Open source emulator for RISC OS. Originally developed for mobile devices such as PDAs and mobile phones.
http://picodrive.acornarcade.com/

Regen
A freeware emulator for Linux/i386 and Windows.
http://aamirm.hacking-cult.org/

retroDrive
Freeware emulator for Windows. Supports 32X. Previously known as Gensx and Vegas.
http://www.tmeekins.com/retrodrive.htm

Virtual Genesis
Freeware emulator for DOS.
http://ourworld.compuserve.com/homepages/JASONMEEHAN/VGEN.HTM

Xega
Freeware emulator for Windows. Supports 32X and Sega CD.
http://www.eidolons-inn.net/tiki-index.php?page=Triton