I mirror my home directory, and I back it up along with my code and web stuff every night to a separate hard drive. The code and web stuff are synced to my "production" web server very often, so there it is well protected. The home directory is also burned to DVD approximately every two weeks, and given to a friend. I am considering putting it on the production web server, encrypted of course.
For things like TV shows, I keep lists of the files which contain info like size and mtime, so that if I lose any of it, I at least know what I lost. It's not worth the cost to back up 4TB worth of TV shows though.
My web server also backs up to my main machine with rsync. There are 5 copies of it. This is mainly to rapidly re-deploy if ever there was a problem.
My firewall does full dumps every couple of nights. There is not really any sensitive data other than a few VPN keys and stuff. The dumps are mainly for rapid re-deployment, just like the web server.
My Windows Vista desktop computer gets knocked down once a month to clone the drive. This way, if I have an irrecoverable problem, I can roll back to a copy that is at most a month old. Nothing critical is stored on the machine. I only have a backup so that I don't have to waste time re-installing from the beginning.