Time Machine is great for keeping a local backup of your system, but if you're rather not worry about having a physical drive plugged in all the time you might want to consider an online solution instead. There are plenty of over-the-air (OTA) backup solutions, though not all are very affordable for a small smattering of system files. Fortunately, there are services like CrashPlan, which offers free back up to multiple place. Read on, and we'll show you how to set it all up.
(Via Mac|Life all.)