Box Office Movies is a PlayBook app that pulls in movie information from Rotten Tomatoes to your PlayBook. Currently it allows you to view upcoming and current movies in theaters in a nice native app. Sadly the app does not allow you to play trailers but hopefully they are working on that. For now you can get the movie poster, cast, synopsis, rating, and more along with an overview of the movie. It covers movies on DVD along with those in theaters.
While some may just prefer browsing the Rotten Tomatoes site you may want to check out Box Office Movies for $0.99 in App World.