One more!
Climateprediction.net is the largest experiment to try and produce a forecast of the climate in the 21st century. To do this, we need people around the world to give us time on their computers - time when they have their computers switched on, but are not using them to their full capacity.
Climate change, and our response to it, are issues of global importance, affecting food production, water resources, ecosystems, energy demand, insurance costs and much else. There is a broad scientific consensus that the Earth will probably warm over the coming century; climateprediction.net should, for the first time, tell us what is most likely to happen.
The Honor Empire has a team setup for climateprediction.net. You can signup for an account here.