Did I mention that BT sent me a free Home Hub before Christmas, but I didn't do anything with it? Hmm, probably not.
Anyway, it turns out that it runs Linux, and BT have released (at least some of) the source only after complaints that they were violating the GPL, and that it can act as a print server. I must try and have a play with it sometime.

http://www.homehubblog.com/
http://hubbub.labs.bt.com/?pagename=viewpost&id=1802
http://www.the-scream.co.uk/forums/t22917-4.html?
http://www.digitalspy.co.uk/forums/showthread.php?t=418613