Tom released an Xbox gamesave manager for Linux:

I'd like to propose you a little savegame manager under Linux. The project is at his beginning. You can list the saves and download them from the Xbox to the PC (w/wo a tarball). For the moment it's just a quick hack (=~ 2h) but I will try to put some good features soon.

You may have to edit the script to change the Xbox's IP. This script is written in perl and released under the GPL license.