ProSystem!

z26 -- An Atari 2600 Emulator

Hataroid is an Atari ST emulator for Android based on Hatari .

Javatari is a multiplayer Atari 2600 emulator written in pure Java with no external libs. Just open it! Needs Java 6 or greater and Atari ROMs.

Steem is an open source Atari STE emulator for Windows and Linux. It runs almost every ST program ever made without any problems. Steem is designed to be easy to use and has many unique features. Whether you want to run great old games, use MIDI apps just like you did on the ST or you have some other, more sinister motive, Steem is the emulator for you!

jGameBase is a fully-­featured retro-gaming emu­lator frontend and game database utility. It is a sister app­lication to the Windows program GameBase (without "j"), the official frontend for the GB64 Collection.

Hatari is an Atari ST/STE/TT/Falcon emulator for GNU/Linux, BSD, Mac OS X, Windows and other systems which are supported by the SDL library.

This is the the Macintosh OSX Port of David Firth's Fantastic Atari 800 Emulator. Ported is the SDL version of the Atrari800 emulator to Mac OSX, and added a full native Cocoa interface, including Preferences, Menus, File Associations, Help and more. It does not require libSDL to be installed separately, but includes it within the application package. It does however require ROM image files from the original Atari systems, which are not included.