Any way to get Time Machine to backup to Amazon Simple Storage Solution?
Dolly Drive is newly-announced software that lets you do TimeMachine backups to "cloud storage". Their docs say the space is their own cloud-based storage space, not S3, so that might be sticking point. But other than that it's pretty much in line with what you're after.

In addition to doing the TimeMachine -> cloud bridge, they also help you duplicate your data to a local drive so you can do fast restores without having to wait for delivery of an cloud -> hard drive dump of your data.

Looks promising. I'm lukewarm on the pricing.