If you have Netflix
If you have Netflix you can watch movies on your computer using their "watch instantly" feature. I have a movie that is in the "watch instantly" selections that I highly reccomend. Check out The Visitor (Link is to Amazon so you can see what the movie is, I cannot link to Netflix)
I recently bought a Roku box that allows me to watch Netflix streaming movies on my TV. The movie I mentioned above I just finished watching on my TV. Because I have the Roku box I do not have to watch it on my computer. The Roku box can be found here: Roku HD Player
If you get one and you have a wireless network you can have it hooked to your TV and working in less than 5 minutes. Once it is setup you can then watch movies on your TV anytime without any additional setup.