Online Backup

External drives for backing up your computer are fine, but these like other drives, can fail. Online backup of your very important files is not that expensive, and it will give you peace of mind.
 

Take a look at Open Drive

We also recommend Dropbox

Always have your stuff when you need it with @Dropbox. 2GB account is free! http://db.tt/B0tCwl9

We use both of these services ourselves.