Hate Android's stock keyboard? SwiftKey 3 is a great alternative for $4. Version 3, which debuted in 2012, features smarter spelling correction and a larger space bar, and the UI is easier to use overall. SwiftKey's word-prediction skills are mostly spot-on. The app learns your writing style, and is very good at predicting which word you'll type next. It even predicts people's names and places you frequent. You can personalize SwiftKey by syncing it with your Gmail, Facebook, and Twitter accounts, and with blog posts.
Many Android phones come with the ubiquitous Swype app, which lets you spell words on a screen keyboard by sliding a finger from letter to letter. If SwiftKey 3 isn't your thing, check out the latest Swype beta here.