DocSets: An Awesome iOS/Mac Reference

DocSets is a Universal iOS app that lets you download and easily browse Apple’s developer documentation. The sets available are for Mac OS X 10.6/10.7 and iOS 4.2/4.3/5.0/5.1 with sizes ranging from around 200MB to 500MB. DocSets also happens to be an open source project available on GitHub. So beyond all that referency-goodness you can poke around in its source code to see how it works, algebraic!