For the Atari 2600 there is Stella, the code name for the VCS 2600. For its succesor the 5200 there is Jum 52. Atari's first homecomuter, the 800 is emulated by Rainbow or Mac800. The Lynx is emulated by Handy (Epyx' name for the Lynx). Even the Jaguar has an experimental emulator, but that has to be started with the Terminal: Virtual Jaguar. Pong can't be emulated, because it used analogue relais instead of microchips. Other Atari Arcade games, like the great Asteroids, can be emulated by Mame.

noSTalgia(Tos-site Only legal when you have an ST
Virtual Jaguar

Emulating Atari VCS 2600

Atari VCS 2600 instructions:

(1) Download Stella, the VCS 2600 emulator from here

(2) Find some games, for instance from the Old Computer

(3) Start the Emulator, find a Rom, and...

presto! The standard keys are the cursor keys and the space bar

Pasted Graphic

The game on the picture is INV+, a game i recommend to everybody. The original Space Invaders might have been a killer APP for the Atari VCS 2600 in 1980, Eric Mooney wanted to make a conversion of SI with 11 invaders on a row, and he did. You can find more information about it here. To play Space Invaders online, go to this page within MacRetro

Emulating Atari Micro Computers

(1) Download Rainbow

(2) Find some games, for instance at the Atari 800 tribute

(3) Start, select a game and yeah!