I've just discovered Movielens - it's a bit like Librarything - but for movies.
You can keep track of movies & DVDs you've seen and review them - or at least just rate them using a star rating. After you've added a few movies it will make recommendations or suggestions of based on the movies you've recorded.
When you search for a movie - it even predicts how you would rate it!! It also has links to Imdb & Rotten Tomatoes.
In Beta mode - they're trying out classifying you according to your viewing preferences - I've wound up in the Rhino Group, which supposedly has other people who enjoy the same types of movies.
Still exploring but it looks like fun!