[GPGTools is now compatible with Mavericks][1]. For those of you that don’t know what GPGTools is, it is the easiest way to setup encrypted email on your Mac. It installs two things:
1. A Mail.app plugin that allows you to toggle signing and encryption on a per-email basis with a couple of nice and easy to use buttons.
2. It installs a GPG Key manager app that helps you create an encryption key, and optionally send it to a key server for others to search.

Once you get this installed it is pretty easy to start sending secured emails. You will be prompted to enter your password to read/send encrypted emails, but that’s just about the hardest part. (The most confusing part is that you have to do a key exchange first, before you can send and receive encrypted emails. That’s why many people, including me, post their public keys on contact pages.)

They have a [nice screencast for new users here][2], and good [instructions to get setup here][3].

[1]: https://gpgtools.org/
[2]: http://support.gpgtools.org/kb/how-to/watch-our-screencast
[3]: http://support.gpgtools.org/kb/how-to/first-steps-where-do-i-start-where-do-i-begin