O.K., so it's not always accurate. But if you need to understand the gist of something, there's no better reference tool at your fingertips than Wikipedia. While there are many Wikipedia apps for the iPhone, this one is the best of the bunch. It automatically searches while you type, which is cool as well as time-saving, and its rendering of the Wikipedia page on the touchscreen is as perfect as you'll find. Upgrade to the pay version, Wikipanion Plus, so you can save articles and do offline browsing.
Next Adrenaline Pool Lite