Atari800 is an emulator for the 800, 800XL, 130XE and 5200 models of the Atari personal computer.
It can be used on console, FrameBuffer or X11.
See http://atari800.sourceforge.net/ for further informations.
Here is a port on Caanoo of version that i had previously ported to Wiz, Gp2X and PSP.
How to use it ? Everything is in the README.txt file.
See http://zx81.zx81.free.fr/ for the source code and a binary version ...