In the old days we backed up to tapes, stored one copy in a fireproof safe on site and just in case another copy went home with one of us developers.

Nowadays I'm working out of my home office and I'm just making redundant copies of my code on another server. I realize that a fire or one well-placed bolt of lightning could cost me years of work. So I'm looking for suggestions... What do you folks use to back up your source code?