BuddyBackup is a free backup program for Windows takes an interesting approach to safeguarding your important files. With BuddyBackup, you can save work - safely encrypted - to your friend's computers. This way, you'll have multiple copies (depending on the number of "buddies" you designate). The software takes regular incremental backups, so only modified data is stored, making this method very efficient.
BuddyBackup - Free Backup to your Buddies