Not out-of-the-box. XBMC on the AppleTV(2) does, though.
[1] Note that I'm in EU-land, where AppleTV is 120 EUR, which is 160 USD. Acer/Asus/Zotac/other nettop vendors do not have the same problem with currency conversion that Apple does.
Apt-getting installs/updates to XBMC rather than jumping through whatever hoops you need to for this is a blessing too.
One downside, you'd need to buy a 3rd party remote and USB-IR receiver and get it working with Ubuntu/XBMC. (At least I did, I think the newer version has one built in).
I used XBMC for years, but boxee is just a nicer experience for an Internet connected HTPC imo.