Hataroid - Atari ST emulator for Android based on Hatari.
Steem Engine - Steem is an open source Atari STE emulator for Windows and Linux.
Stella - Stella is a multi-platform Atari 2600 VCS emulator released under the GNU General Public License...
Z26 - Z26 is one of the best emulators for the Atari 2600.
jGameBase - jGameBase is a fully-featured retro-gaming emulator frontend and game database utility.
Atari800Win PLus - Windows port of Atari800 based on the original Atari800Win v2.5c sources.