Bacula is an excellent backup solution available for the BSDs, Linux, Mac OS X, Windows, and other operating systems.
As the original contributor of Bacula's network encryption support, I recently volunteered to implement on-disk backup encryption -- with one catch. In exchange for implementing data encryption support, I would like the Bacula community to donate $3,000 to the Electronic Frontier Foundation.
To quote the official announcement: "Can your company contribute $250 or $500? How about $100? And if your budget is really tight, why not forego a couple of fast food meals and contribute $20?. Bacula is a community project, and this can be your way of helping make Bacula an even better product for the good of the whole community."
Information on how to donate can be found in the official announcement.