My go-to place for movie listings – Flixster - Showtimes + Tickets Review

Can see what's out there listed by theater or by movie release date, etc. Integration with Rotten Tomatoes is very valuable. I only wish it didn't exclude certain (smaller) theaters (who apparently have to pay to be listed -- "bad tomato" for Flixter for that).
Review by Steve Davidson on Flixster - Showtimes + Tickets.