Wikipathia is a free app in the Android market that gives you two terms or concepts; then it is your job to essentially connect the dots, making the shortest path between the two things using the massive amount of Wikipedia articles as your links. Once you click start, you are given a Wiki list of everything that comes up in common with your starting term. Clicking on a new term will then give you a new list, hopefully leading you closer to the term you are trying to reach. Each time you click on a new term it counts as a path. The goal is to connect the two original concepts with the fewest number of paths.

You can download this application from the market here.

When you are give your pair of terms you can ask for new endpoints which will give you an entirely new pair of terms or you can simply flip the two endpoints you have, which the game recommends as being a strong strategy.