App4Mac has just announced Twin 1.0 for Mac OS X (US$39.67, €29.00), an online backup solution that works with all sorts of servers: FTP (all varieties), WebDAV, Amazon S3, and even MobileMe. Unlike many of the other online solutions, Twin claims that it retains all the Mac OS X file metadata, ACLs, and privileges, and your data is kept safe with AES-256 "Jack Bauer quality" encryption. In addition to the online backups, you can use Twin for backing up your files to local drives and have the backups begin when the external drive it plugged in.
I'm impressed with the powerful scheduling capabilities of Twin, which include a way to use logical operators to determine exactly when backups should proceed or not. Having an offsite backup is that extra bit of security that every Mac user should have. Check out the gallery below for some screenshots of the app in action. You can also download a free, limited-capability trial of Twin if you're interested in kicking the tires.