BackBlaze for Mac OS X is out.
I've been using BackBlaze (in addition to Time Machine) for about 4 months now, and I've been really happy with it. At $5 bucks a month it's a steal, and I'm backing up both my wife's laptop and my desktop (with a combined total of 113GB).
I had trouble installing BackBlaze on my desktop when it was in private beta, but I talked with support, got the issue fixed (I've got some weird disk configurations), and it has been a breeze ever since. My house can burn down and take my Time Machine backups with it, but the really important stuff is still safe are reachable online with BackBlaze.
Peter Cohen has a review of it for Macworld.com as well.