Crackle, from Sony, is a free universal iOS app that's built to stream plenty of free-to-view movies and TV shows. If you don't mind ads at the beginning and more in the middle of the programs and you're OK with the app's limited selection, it's worth a look.
Not surprisingly, a lot of the movies are from the Columbia Pictures catalog, since Sony owns those titles. There's a smattering of good movies (The Gods Must Be Crazy and It Might Get Loud, for instance) and then there are a slew of Godzilla movies and martial arts movies that may or may not strike your fancy. The catalog includes old Three Stooges shorts, and TV shows like Seinfeld. Movies expire off the app's catalog, so the selection will change over time.
There are some nice features: closed captioning and AirPlay are both supported, and when you leave the app and come back your movie will resume playing where you left off. It worked well over 3G, and the films are licensed for Canada and the U.K as well as the US. Quality of the prints was good, as it should be from an app provided by a movie studio.
It's not the most stable app I've used. I had 2 crashes in one test. Then I tried it later in the day and it worked fine. The app has not been updated to take advantage of the increased screen real estate on the iPhone 5.
I would classify Crackle as "airportware," an app to pass the time while you're waiting for a flight. If you're not a Netflix, Hulu or Amazon Prime subscriber, Crackle is a good free alternative; depending on your TV provider, you may also already have a free subscription to the EPIX app, which offers a much wider selection of recent and classic films.
Crackle requires iOS 4.2 or greater. A recent update fixed some bugs (but apparently not all of them) and redesigned the GUI.