I recently came across a great solution for small business looking to backup to the cloud at the lowest possible cost. The solution is open source data deduplication software called OpenDedup.
The design would be a Linux VM running OpenDedup onsite with a mounted S3 bucket. Backup applications write to this volume either over iscsi or NFS. The data is dedupped and only the changed blocks are written to S3.
The big benfit is the dedup feature. On a nightly basis only the changed blocks have to be uploaded over small bandwidth Internet lines to S3.
If all goes well Blumetech will use this same software for our AWS Backup.