Steve,
Also check out Google video as I've even been surprised at what's out there. More older movies than current but still surprised. Just recently watched a movie from the early 90's that I missed at the time called Mindwalk that I enjoyed a lot. No, it's not a sci-fi thingy either!
If you like documentaries, check out
TopDocumentaryFilms as they have a lot of programs and documentaries like you'd find on National Geographic, History and Science channels so for the kids educational stuff, it's a good resource. Now it will include stuff like Micheal Moore's films, various conspiracy films and of course the ever present with us allegations of space aliens and Area 51 stuff so as a parent I'd use strong parental oversight. As much absurd stuff as you'll see, there is also as many educational and family programming as well and the science catagory is loaded with good stuff to watch. My son and I love watching stuff here and I learn just as much as he does and it really provokes thinking and learning for both of us.
I got a 36" flatscreen for my computer and I've found so much on the net these days that I'm rethinking cable altogether.