If you learn by drawing or looking at visual images, mind mapping can be a great study tool. The easiest app I've found for it is called Xmind.

Mind mapping aims to prevent those cranial logjams through a process that gets the ideas out quickly, without needless organizational burdens. XMind 2008 Pro (version 2.3) stays true to the mind ...

XMind -- a powerful, Java-based mind mapping and charting application -- has been open-sourced (it's free!) with version 3.0. While it's not my absolute top pick for mind mapping, it ranks up ...