I just use either SuperDuper or Carbon Copy Cloner to make an image of my machine, and store that off on an external HDD. I use it moreso for recovery purposes, not even so much content - if the content is a bit outdated I don't care. To complement this, on a monthly basis I back up my actual current content to a DVD-RW. 4.4 GB is more than adequate (for now!) for my entire iPhoto library, my Documents folder, Mail folder, etc., but I am by no means a power user, and I run a tight, clean Mac - I keep it neat and tidy, therefore I don't have a lot of junk to back up. And for things that don't change much (movies, music, software), the HDD backup is fine.