[Note] Currently only works with Windows Vista and 7, XP support being added soon.
I know there's a couple of backup utilities out there, but I recently put together a very simple tool that lets you easily backup your worlds. One feature that I've included, and am working on improving, is a timed save feature that allows you to input a time interval and automatically back up your selected worlds at that interval. Another feature I implemented was the ability to pick and choose which worlds you wish to save - so if you are messing around in a couple, you are still able to choose exactly which will be backed up rather than having all of them automatically saved.
I've tried to learn from the good and bad of the other tools out there - and while mine is not as robust as a few of them (with online syncing), it does it's job very efficiently. The utility will open, scan which worlds you have, and allow you to pick among those saves.