There are several sites to (text) preview movies, here are my favorites: http://www.denofgeek.com/movies/ (action) http://twitchfilm.com/ (thriller/horror/asian) http://io9.com/ (science fiction)

For watching the trailers I prefer Apple's site: http://trailers.apple.com/trailers/

My girlfriend always seems to know the plot of every movie. For a while I was wondering when she was finding time to sneak off to the theater, and why she was doing it without me. Her secret was just that she watched just about every movie trailer at apple.com.