Lately I've been looking for a utility to backup my Mac automatically to a network share – which is actually on a PC. Of course, I don't actually like buying software, so I was hunting for something with the 'free backup utility' phrase associated with it ;).
I found SilverKeeper, a free Mac backup application. It has a very (almost too) simple, easy to understand interface. You set your source, destination, and schedule when you want it to run. You can set up different backup sets from within the application. A backup set is basically just the source to backup and the preferences to go with it. You can choose to exclude certain directories (I don't backup my music).
I have found it a little slow in backing up to a network share. I'd almost prefer something that backs up to an encrypted, compressed file, which I can then quickly transfer over the network. Though I suppose that would take out some of the automation, now wouldn't it!