In November, we covered installing Boxee on AppleTV using atv-usb-creator. [Danny] has written a tutorial on installing Boxee, XBMC, NitoTV, SSH access, and external USB hard drive support. His method installs most of the software via the USB patch stick, then uses the SSH support to enable the external drive and install NitoTV. The tutorial lists a Mac running OSX 10.4 or newer as a prerequisite but there is now a Windows version of atv-usb-creator. According to their Google Code page Linux support for this package is on the way.
[via AppleTV Hacks]