- Atari Archives atariarchives.org makes books, information, and software for Atari and other classic computers available on the Web
- AtariWiki The AtariWiki is a collection of Information about the Atari 8-Bit computer line mainly intended for programmers. It covers topics specific to the Atari 8-bit computers, but also generic programming topics like the 6502 line of processors, pProgramming languages available for the Atar8 8-bit machines and generic programming tips and tricks
- mads Assembler and Pascal comiler
- ASAP ASAP is a player of Atari 8-bit chiptunes for modern computers and mobile devices
- xebin Atari XL/XE Binary File Utility
- xedisk Atari XL/XE Disk Image Utility
- fastbasic FastBasic - Fast BASIC interpreter for the Atari 8-bit computers
- Fusion-Forth A Forth interpreter/compiler and IDE for Atari ST
- libcmini small footprint C standard library for Atari ST and m68k-atari-mint cross compiler toolchain
- 8bit-unity 8bit-Unity is the cross-platform C language SDK for the CC65 compiler, which allows writing your game only once, and then deploy it on all those platforms
- Atari8GUI A Graphical OS for the Atari 8-bit
- Renderific An SVG renderer for Atari 8-bit computers, written in Turbo-BASIC XL
- Video everse engineering Atari 8-bit video
- sio2arduino is an Atari 8-bit (800/XL/XE) device emulator that runs on the Arduino platform
- Altirra Altirra, an 8-bit Atari computer emulator
- Atari 800 Atari800 is the emulator of Atari 8-bit computer systems and 5200 game console for Unix, Linux, Amiga, MS-DOS, Atari TT/Falcon, MS-Windows, MS WinCE, Sega Dreamcast, Android and other systems supported by the SDL library
- Atari++ The Atari++ Emulator is a Unix based emulator of the Atari eight bit computers, namely the Atari 400 and 800, the Atari 400XL, 800XL and 130XE, and the Atari 5200 game console
- javatari.js Javatari - Online Atari 2600 Emulator
- Sim2600 Visual6502.org transistor-level simulation of the Atari 2600 game console
- Hatari 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
- Arkos-Tracker-2-ST Atari ST version of the replay source for Arkos Tracker 2
- Atomchess-6502 Toledo Atomchess for Atari VCS/2600
- emutos EmuTOS is a Free operating system for Atari ST computers, and more
- freemint Unix-like kernel for Atari ST and compatible computers
- pop-a8 Prince of Persia port to Atari 8-bit
- Atari_ST_Sources A large repository of Atari ST (and family) source code