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.
This is an open-source implementation of Elegitimizer.com's "elegitisigner" specification. An easily implemented validation mechanism to help eliminate illegitimate e-mail or Spam. Elegitisigner features a well documented web of trust model.