Currently Being ModeratedJan 20, 2013 8:47 AM (in response to JS O)
I would suggest CarbonCopyClone ($40 download) to backup an external drive. It allows you to select the source and destination drives, and makes bootable clones which I would suggest doing for your intern drive. A bootable clone is a good "usable backup" when your internal drive fails (it will eventually fail).
SuperDuper also clones, but does not save the RecoveryPartition like CCC does (at least so is reported).