Twin is the most flexible online backup solution for Mac OS X, compatible with most Internet servers:
FTP, FTPS, SFTP, WebDAV, Amazon S3, MobileMe. It even supports offline backups to external drives.
Twin is a true Mac product that preserves Finder info, resource forks, ACLs, Privileges and comes with an elegant user interface and a powerful assistant. It also provides numerous high-end features like AES-256 encryption, efficient bz2 compression, powerful exclusion rules and scheduler, support for splitting large files during network transfers, network-error recovery, individual digital signature for backed up files, multi-cores machines optimization and much more!