Last month I bought a 2.5" laptop hard drive enclosure and an 80GB drive to go with it. Today I finally got working my backup solution using it. I'm using rsnapshot on my Powerbook under Linux to do the backups, and TrueCrypt to encrypt the partition that I'm backing up onto. I set it up to not only back up my home directory under Linux, but also my homedir under OSX, my Techhouse directory, and my CS system directory.
I set it up to make a snapshot on a daily, weekly, and monthly interval basis. It will try to run every day, but it will only succeed if the drive is actually mounted. That's okay; I don't actually need it that often, but there's no harm, I guess. I can also perform snapshots manually if I want. And I can carry the drive around, so that I can read my backups on any machine with TrueCrypt installed.