If you're into HTPC's, this might be something interesting to check out. You could do the Media Center Microsoft version of Vista or XP (soon Windows 7), but there are open sourced alternatives out there that work pretty well and do a bit more than Media Center Editions of Windows.
Some of the major features it does:
TV (Tivo like functionality)
Videos and DVDs
They do have a large library of plugins for their 1.0 version which includes some streaming from the net (Like CBS for example).
The thing I don't like is it does not support DLNA at the moment (version 1.0), although you could point it to your files on your network, but that won't allow you to use PlayOn or other cool online streaming functions. Their version 2.0 which seems to have been in development since around 2007 still hasn't really got to far as they are fixing version 1.0 and stabalizing it still. It seems their version 2.0 has an alpha or beta out (not sure, was checking forums you might want to look into it more) and that it supports DLNA, but since it's alpha obviously not in the best shape.
It still is a cool project, and with their V2 if it can come out of alpha / beta might really be a great HTPC project to use. I will see about posting a few more HTPC like applications in the coming days for those interested in that kind of tool.