I am thrilled to learn from a comment left here by Ken, that Leonard Maltin's Movie Guide is now available on the iPhone and iPod Touch. I bought mine from the App Store for $4.99, which is a third of what the book costs.
The advantages of it over other applications is that you don't have to be connected to the Internet to look up movie details. You get plot summaries, star ratings, cast and director. You can search the database by title, cast, or director to get filmographies. I do this all the time when I'm out with friends. We'll be talking about movies and they ask me what other movies has an actor been in? What other movies has someone directed? They think I'm the movie expert, and I keep them impressed by using Leonard Maltin's Movie Guide.
Another advantage is that you can create your own custom lists or add to Favorites or Movies to See which you can backup online. There's also a button to add movies to your Netflix queue (requires an Internet connection).
I've been waiting for this ever since I gave up my Palm T|X. A good movie guide was the only thing I missed about that Palm. I left a note on Leonard Maltin's Web site, asking that they make an app for the iPhone. I reckon I wasn't the only one who wanted it. Now my iPod Touch is complete.
If you don't have iTunes or an iPhone, check out the developer's Web site for screenshots and more info.
P.S. No one paid me or gave me anything to write this review.