Windows/Mac/Linux: Keep your data backups under your control with CrashPlan, a handy backup tool that facilitates local and friend-based remote backups.
Like previously reviewed Cucku Backup and Zoogmo, CrashPad supports peer-to-peer backup solutions. CrashPlan can back up to multiple locations including local disks, networked disks, remote server space you have access to, your friends' remote computers, and (in a fashion similar to Mozy and Carbonite) to CrashPlan's remote backup servers if you subscribe to their service.
Assuming you have a remote location (a personal web server, friend's computer or work computer) you can use as your backup location you'll be in business. Your remote data is encrypted so you don't have to worry about your friend discovering you have the largest collection of Hello Kitty videos outside of Japan.
The setup and user interface for CrashPlan are straight forward, you shouldn't have any trouble getting things up and running. Most people won't find that they need the additional perks that come with an upgrade to the premium service, which makes CrashPlan an appealingly free option for personal backup. CrashPlan is freeware and available for Windows, Mac and Linux.