I use a nice OS X app called Arq which does encrypted backups to my own S3 bucket. Since I only have a few GB of stuff that warrants offline backup (git repos, etc) the ~$0.25 storage fees per month is well worth the convenience.
For Linux, try Duplicity (which I mentioned in another comment): http://duplicity.nongnu.org/
Both are open source and have similar features to Arq (including Amazon S3 support).