jQuery is pretty straightforward: once you've mastered the basic usage patterns, all that's left to do is memorize the entire API... or have a good reference on hand!

This app served as an "on-the-go research tool" for my soon-to-be (or perhaps, recently) released book, jQuery: Novice to Ninja (which you should rush out and buy). It's built on top of the snazzy jQTouch library/plugin. If you want to make quick-and-easy web apps for the iPhone, then check it out.