I’ve been playing with GNU Privacy Guard, a completely open source replacement for PGP. Brendan Kidwell has a guide which gives a good basic introduction to GPG on Windows. Enigmail lets you incorporate GPG into Mozilla’s mail client as well as the standalone Thunderbird mail client. You can search for a person’s key at http://www.us.pgp.net/pgpnet/pks-commands.html. You can find my public key here.