This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here. While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will be closed per the help center.
Backup is incredibly important. Obviously there's no best backup tool, but a comparison of the options would be very interesting.
- Graphical Interface? Command line?
- Incremental backups?
- Automatic backups?
- Install method: In standard repositories? PPA?