I went through the same thing a few weeks ago and found this free one from Lacie:
http://www.lacie.com/silverkeeper/
It's called silverkeeper and does exactly what I need it to. You select the source (and set exceptions if their are folders under the source you don't want to backup) and the destination, and then let it rip. You can then save those settings as a "backup set" so the next time you launch it, you just need to click the "go" button.
I should note that it will work with any destination and that it is NOT lacie-specific. My external drive is actually a SimpleTech...