Mac: Text Expansion can save you hours of typing by typing common phrases and text snippets for you, but most Mac text expansion software is pretty costly. DashExpander is not only free but it's really good, too.
DashExpander runs in the OS X menubar and pretty much keeps out of your way until you press Option+Space (or change that shortcut to something else). The interface can be a little strange to use, but you simply type the name of the snippet you want to search for. What's pretty incredible is that you can create snippets that don't just expand into full text but also act as fillable forms. If you want to use these snippets on multiple computers, DashExpander lets you save its library anywhere (meaning you can sync it with Dropbox or a similar service).
While DashExpander isn't going to provide you with the vast number of features of some other text expansion apps, it's nonetheless a very compelling option that costs you absolutely nothing. You might find it a little awkward to use at first because the interface is a bit different from what you'll normally find on a Mac, but it's worth it. It's a really nice app and you can't beat the price.
DashExpander (Free) [Mac App Store]