I do a monthly offsite backup. I use rdiff-backup for plain text and 7z with encryption for data I want to keep private, but I am on the lookout for more efficient solutions. I looked at bup, but two things stop me from using it: no encryption, and inability to delete old backups to reclaim space. To me, attic ( https://attic-backup.org/ ) looks attractive so this is what I am going to try soon.
I've used rdiff-backup daily for years, but recently needed to store backups on machines I don't control, so I gave duplicity[1] a try. It encrypts, doesn't need to be installed on the target host and is simple to use if you're already familiar with rdiff-backup and gpg. Test restores were simple, but were all first generation, so not really a good test (but there are hints you'll want to prune backups to one month's…
I use duply for unattended, automated backups.