Tarsnap is an online service where you can securely backup your data. It is maintained by Colin Percifal, an ex FreeBSD Security Officer.
Tarsnap is a secure online backup service for BSD, Linux, OS X, Minix, Solaris, Cygwin, and probably many other UNIX-like operating systems. The Tarsnap client code provides a flexible and powerful command-line interface which can be used directly or via shell scripts.
Linux Journal has a 10 page article on Tarsnap in its latest issue.
Collin recently announced you can now pay by credit card for the Tarsnap service, in addition to Paypal.