Toast 6
Even better than that is the Deja Vu program that it comes with that can schedule automatic backups to either removable media or other external drives and even other drives on your LAN.
After my hard drive went bad on me last week I'm realizing that even if you have your data (images, contracts, etc...) backed up there's still a good bit of down time in getting your system back to how it was. For me the Library folder is key!!! It contains your calendars, emails, bookmarks and all that good stuff.
Back it up!
