It's bad form to dig up old threads, but something happened that will interest at least a few people here.
Yesterday, someone announced that he had found a way to access the command line on the Archos 605/705/604. The devices are supposed to be locked down so you can't do this.
Apparently, you can execute command line arguments by setting up a new Wifi network connection and setting the command line as the password.
Here are his instructions:
http://code.google.com/p/arcwelder/
It's also being discussed here:
http://forum.archosfans.com/viewtopic.php?t=11144
I don't have one yet. The Kindle was released while I was waiting for the 705, and I also have a rule of only one new gadget at a time. But the thought of a 7" tablet running Linux is seriously tempting.