If you're using windows, I'd reccomend SyncBack from 2BrightSparks to do the backups. Works perfectly and I think it's freeware.
This is my plan to do backups:
Local: Backup to an external harddrive (WesternDigitial EssentialEdition 500GB) connected to a Linksys Network Storage Link ( http://www-nl.linksys.com …Wrapper&lid=0443374557B44
) which is connected to your router.
Off-site storage: Same setup, just place it in a friends house.
Great thing about the Linksys Network Storage Link is that it's running on Linux and thus able of running self-written scripts. I think it's fairly easy to write a script which uploads the data of your 'Local external HDD' to the one at another place.
Sure, it takes a while to upload 2gb in RAW's or so and you'll need an internet provider who doesn't charge extra for uploading or downloading alot of data, but once it's setup you wont have to worry about it 