Backup is a system utility for Linux and OS X which allows you to easily model your backup system using a nice Ruby DSL. The greatest thing about Backup, aside from the fact that it Just Works, is that it has built-in support for just about anything you would want to do.
It handles compression, encryption, cloud storage, splitting, syncing, notifications, logging, and on, and on.
With all that functionality, you might expect Backup to be overwhelming to get started with. Not so. It also has nifty generators which spit out documented model code so you can learn and tweak as you need. If that's not enough, there is a Getting Started page and a very useful wiki which explains, in detail, all of the subsystems.
Backup is MIT licensed and hosted on GitHub.