Rotten Tomatoes has an API
If you want to get info about a movie (e.g. rating, cast, etc.), there is imdbpy, which collects data from IMDb. I just found that Rotten Tomatoes has an API too: http://developer.rottentomatoes.com/.
Update (20150622): about two weeks ago I asked for an API key. I’ve got no response since then…
Update (20150623): I got an answer from them! Here it is:
Thank you for your interest in the Rotten Tomatoes API. Unfortunately, we are unable to grant access at this time. Due to changes in our syndication program, we're currently only offering free API access to domestic students. This may change in the future as we add additional tiers to the program. -The Rotten Tomatoes Team