Foldit is a multiplayer video game with the goal of solving unsolved structural biology problems. It's an example of what Louis Van Ahn calls 'Games with a Purpose'. Recently Foldit players helped solve the crystal structure M-PMV retroviral protease.
Foldit is quite playable and enjoyable in its own right, at least on the training levels I worked through. One of the pleasant surprises is that players are given a variety of automated tools for energy minimization - they don't need to rotate every bond themselves. The game also does an excellent job of presenting the goal in a graphical way.
These and other factors move the gameplay into the level of thinking and strategy - and a genuinely fun experience.