Do you want to do actual geography and archaeology from your computer? Do you want to be part of an adventure to locate a lost tomb of the founder of the largest empire the Earth has ever seen? If you do, then sign up for National Geographic's Valley of the Khan's Project! National Geographic is having users tag images of the earth to tag features, both human and natural, in order to help identifying promising sites which match potential descriptions of the location Genghis Khan's tomb. (Hat tip: iRevolution)
This remote sensing opportunity will not end with you fighting Nazis, looting ancient treasures, and getting the girl. However, it will give you bragging rights allowing to state you helped National Geographic in the search for the lost tomb of Genghis Khan.