I received an email from Eric Warnke at Backup Box a little while ago mentioning their new service. Backup Box is a general backup service for online resources. It can backup a Web site or FTP, GitHub, etc. to Dropbox, FTP, GitHub, etc. It's not a real time sync, but rather a scheduled backup. It's kind of like Ifttt but designed specifically for backups between online services. It looks very cool and I'm just now starting to play with it.
The same list is available as a destination. The pricing model is interesting too. Manual or monthly backups are free. The prices increase based on the regularity of transfers with daily being $10/month. It's worth a look since, even if I already have my own home-grown solution.