NASA TV
It's not like the Discovery Channel, or The Learning Channel, or the Sci-Fi channel. There are few documentaries, and a lot of annoying repetition of 2-minute vids. Until the space station was manned, there wasnt much of anything on NASA tv, and these days it is still kinda boring IMO. You can watch NASA tv on the internet. Decide for yourself:
http://www.msnbc.com/m/lv/default.asp