E-mail encryption? no problem. Ciphire Mail has you covered

CiphireMail is only in its beta stages, but it has support for Windows, MacOSX and Linux. If you wish to know how it works, here’s the overview.
It’s not a difficult install, and works in the background like Norton antivirus. Pretty useful for those pieces of e-mail that you don’t want hijacked. BoingBoing sings its praises here.