Hulu.com is an online video service: Visit the Web site, and you can watch episodes of TV shows and movies online. For free!
Say you missed last week's episode of House. Just head over to Hulu and watch it online. Feeling nostalgic? They have lots of old TV shows too: Alf. The Addams Family. They have tons of movies too. It's not an all-inclusive archive, but a lot of the shows I watch are on there. Check it out.