I am finally going to do a cloud backup of my system for extra redundancy, and the CrashPlan system seems to be well regarded and recommended by many.
Easiest way to set this backup up is to run the client software from a windows machine. I have a Win7 VM running 24/7 anyway, so that is a perfect place to setup the CrashPlan software.
To get the CrashPlan software to read and backup a NAS drive, read the following links:
They all talk about the same technique.