One of the tried and true best ways to study and retain information is to re-write the content - whether it be lecture notes, textbook facts and figures, or whatever - down again on paper. We can do one better than that, can't we?
A wiki is a great venue for bringing this idea into fruition without having to deal with all of that paper. Start with a blank wiki on a platform such as PBWorks or another lightweight phone friendly version such as Wikka, and begin filling in your class knowledge.
Instead of cramming in study time at the last moment before midterms or finals, break it down into small chunks and when you have a spare moment, bring up your wiki on your phone for a short refresher. When you get larger amounts of time, fill out the wiki with class information - this method helps you retain facts much better than just reading.