iPhone users have a lot of tv apps to choose from,
Netflix is probably best if you dont mind paying. The tv/movie on demand service is one of the best streaming services on the web let alone iphone. There are movies and TV shows on Netflix as well.
Remote Control suitable for a wide selection of TV's and DVR's and lets you use your iphone to control your viewing pleasure.
Imdb The internet movie database is probably 'THE' place to look for movie info, including actors, plot summaries, synopsis etc.
iTv Use this app to look up local movies and TV listings. Plus you can see what everyone else is watching as well.
TV.com You can watch streaming TV on this app, albeit limited but if the TV show you are looking for is available then heres a good place to view.
TV Guide Does what it says, a local TV listings guide and has a few extra features such as favorites etc.
Direct TV For viewers with a iPhone and direct TV you need this app. TV listings for 2 weeks into the future and set your DVR to record shows from wherever you are.
DVR remote This app is designed for TiVo and can be used as both a remote and TiVo mobile. Set your TiVo to record whilst your somewhere else.