I've been playing with Boxee. Boxee is set-top-box type software that can be loaded on Mac, Apple TV, Linux, and Windows (not quite there yet). It does a very good job of integrating multimedia with linear or broadcast type television.

Boxee is mostly open source according to this Wikipedia article. The closed source portion of their distribution provides the social networking functions in Boxee.

Boxee supports and integrates with a number of Internet based TV services of which Hulu is one of them.

While Boxee runs great on my Mac laptop, I find watching TV on on the small screen to be a bit droll. I'm looking forward to someday having a Boxee Box - a set-top-box that runs Boxee. They aren't being made yet but I'm still hoping.