I have recently acquired an X.509 S/MIME email digital certificate (free, natch...) from the Thawte freemail program, which allows me to digitally sign emails, and also allows other people to send me encrypted email (assuming they have a certificate too.) If you ever want to instigate properly secure email with me, just request a signed email from me and then you can install my public key in your mail client. Woo hoo.
I don't have any use for all this crypto stuff, but I just find it irresistibly geeky...