For car use, SonicBlue is getting rid of Empeg (Linux)
basically, they (SB) don't want to compete with big car audio companies, so they're selling off their stock of RioCar (empeg) car HD MP3 players. They say they're going to continue to develop the software, which may prove to be true, since they claim they're going to stay in the car audio biz by doing software, etc for the big companies.
Anyway, it runs Linux and is hackable, comes with Ethernet, USB, room for a second HDD, remote, and AC power supply. Clearance pricing is $300 (20G) to $500 (60G)
Overall, a very different beast from the Archos -- but it seems much nicer if you primarily want a unit for a car. Since that matches what I've been looking for, I've got one on order. But, if I were going to buy a portable MP3 player, I think I'd go for the Archos due to its combination of size (only iPod is smaller; Creative, Neo, DLink are MUCH bigger), capacity (20G available), and price.
Tony