Derek found this description that seems better than Jungle Disk. I noticed the Jungle Disk app was trying to connect to weird non-amazon IP addresses, so I didn't feel comfortable using it.
http://blog.eberly.org/2006/10/09/how-automate-your-backup-to-amazon-s3-using-s3sync/
This looks nice, being able to store stuff for $0.15 per GB per month.
