Freeware: Gpg

GPGMail 1.0.2GPGMail is a plug-in for Mail.app, providing a front-end to Gpg for some operations. GPGMail extends Apple's Mail/MailViewer application and allows you to read and send PGP authenticated and/or encrypted messages.

GnuPG 1.2.4GnuPG security encryption framework. Mac GNU Privacy Guard (Mac Gpg for short) is, after a fashion, the Mac OS X port of GnuPG, licensed under the GNU GPL.

GPGPreferences 1.2GUI to edit GnuPG options file. GPGPreferences can edit GnuPG's options file with a GUI preference pane Mac GNU Privacy Guard (Mac Gpg for short) is, after a fashion, the Mac OS X port of GnuPG, licensed under the GNU GPL.

EntourageGPG 1.3b5\Allows encryption of your Entourage email. EntourageGPG is a front end for Gpg inside Microsoft Entourage. Gpg , or GNU Privacy Guard, is an OpenPGP-compatible free public key encryption tool.

Crypto Anywhere - OpenPGP Edition 2.0Secure Email. Standalone or integrated with Outlook. Can decrypt and encrypt messages to friends using PGP, OpenPGP, SecExMail and many more. Crypto Anywhere allows you to make a travel floppy which can be used in internet cafe's or at work. Free.