Before I get to the nitty gritty, this is relatively unstable port at this time, however it DOES work.
At this point (and I am working on it) if you minimize it, it is lost forever (think killall), the "-" button brings up the console but if you didnt run it from xterm your hosed and then you can not close it (again killall) (but I left this because it is useful to me during testing).
Currently you need to put the roms (which you will need to find on your own, but you might want to look at http://atari800.atari.org for ideas on what to use) in /media/mmc2/atari/ROMS and this is also where I put the HD, DISKIMAGES and various other files I am using. This is configurable in both the .cfg and the launch script file to be pointed where ever you want.

the .cfg file sets most of the useful settings for you but the launch script is necessary (at least at this point) because I can not figure out how to put some of those options in the .cfg file. The most important part of this script is the floppy it mounts (which is the 'game' or dos disk you want to boot to. There are options for HD's but I didn't set them up.
Without a bluetooth keyboard you need xkbd to do much outside the joystick I have configured now and I would recommend Addison's x.xkdb template as it fits perfectly in both windowed and fullscreen modes.

OK never mind all the rest of this and see a few posts down for a real honest to goodness .deb..


OK so without an further delay here is a tarball of the files you need, it 'should' uncompress them all to the proper locations, but in case it doesn't here is the TOC of the file...
Nokia-N800-51-3:~# tar -tvf atari800_2.0.3-1.tar
-rw-r--r-- 29999/29999 524 2008-03-24 23:08:30 home/user/.atari800.cfg
-rwxr-xr-x 0/0 192 2008-03-27 10:00:05 home/user/atari.sh
-rw-r--r-- 0/0 2941 2008-03-27 10:00:37 usr/share/pixmaps/atari.png
-rw-r--r-- 0/0 270 2008-03-27 10:01:56 usr/share/applications/hildon/atari800.desktop
-rwxr-xr-x 0/0 427088 2008-03-24 18:49:14 usr/bin/atari800

The file is attached (remove the .deb on the end as it is the only way I could attach it...)and good luck

I will keep plugging away at it and will post revisions every time I make a significant change.

-John