Konfidi is a trust framework that uses topical trust values from a social network of authenticated people. When you receive an email from someone you do not know, but he/she is in the network, Konfidi will compute an inferred trust value for you.
Not the greatest thing since Sliced Bread, it IS Sliced Bread. This project is a series of network tools and a network development SDK, with big hopes, and too little time to code it all.