Mozy does online backup just like Carbonite, but they also have a client for Macs. Both Carbonite and Mozy do encrypt your data, however a lot of online backup companies do not. Neither of these services are free, and do have an annual fee, which is very reasonable.
The most important about these online backup services is that they allow you to store your data off-site. So if, God forbid, a fire destroys your computer or data, you know a copy of your files are safe and secure on Carbonite or Mozy’s servers. Or, if your hard drive fails, or your CDs or DVDs don’t work, it’s a definite peace of mind to know your data is safe.