Today's Seattle Time Technology section had an article on Using an HDTV as a video monitor. I've done this once or twice to display slide shows with a borrowed laptop (I only own a desktop). Here is another link with a bit of information
But since I got a new PC in December, I just happen to now have an older desktop that I'm not using. I'm thinking about giving this a try. I'm going to need to get some more equipment (router, wireless keyboard, mouse, etc) first but it might be pretty cool. I might be able to play downloaded DVDs from Netflix on it.
Another option is to use a MacMini. A audio-visual enthusiast I work with uses a MacMini for his movies, etc.