ST

Castaway - An open source SDL using emulator for Linux and Windows/Cygwin.
sourceforge.net/projects/castaway/

FAST - A freeware emulator for DOS.
fast.emuunlim.com/

Hatari - An open source emulator for Linux, Mac OS X, and Windows using the SDL library.
hatari.sourceforge.net/

The Little Green Desktop - The largest Atari ST/Emulation Resource on the Internet.
www.atari.st/

NoSTalgia and PowerST - Features NoSTalgia an emulator for MacOS X (older version for CarbonLib and MacOS 9 available) and PowerST a suspended emulator for MacOS 8/9.
users.skynet.be/sky39147/

SainT - A freeware emulator for Windows.
leonard.oxg.free.fr/SainT/saint.html

Steem Engine - A freeware emulator for Linux/i486 and Windows.
steem.atari.st/

STonX - An open source emulator for Unix/X.
stonx.sourceforge.net/

WinSTon - Source code of a not anymore available windows emulator.
sourceforge.net/projects/winston/