"JogNog, a website that provides competitive learning games that motivate students in grades 2-12 to learn, has opened up its library of elementary and middle school content to teachers who want to create games that match their specific lesson plans" via eschoolnews
The BizWorld Foundation's programs provide a platform for the critical thinking and teamwork students need to become productive members of society. Free downloads and kits for purchase.
Mechanisms and guidelines for the development of games (board games), more specific games that can be played in social environment. The building block links gives you some detail information on mechanics.