All my software/serials and misc stuff is backed up to CDs, even freeware I backup in case the author decides to pull it off or start charing, so I can still use it in the event of a clean install.
Files that always change, such as my websites are backed up regularly, its all automatic so all I need to do is check the log email account to ensure the backups ran successfully. They're backed up on several locations on the server and rotated a few days deep, and a few weekly ones are kept as well. I try to backup the most important stuff over 2 HDDs on seperate machines.
I've been thinking of getting a dvd burner so I can start doing non magnetic backups. Safer against a giant magnetic pulse or something, if ever there happend to be an occurence of one. You never know.