You know how everyone is always telling you that you need to back up your data? Time Machine makes it painless and automatic. You need another disk drive to put the backup on, but those are dirt cheap these days; we got vakkotaur's parents a 500 GB USB drive for $139 that will hold all of their backups for decades. Once you set it up, you never have to worry about it again. It happens automagically, in the background, and you don't have to do a thing.
Restores are simple, and use an intuitive interface that lets you move backward and forward in time to the point you want to restore from. Once you pick a time, you select the files you want to restore and tell it to go, and it does the rest. The system keeps hourly backups for a day, daily backups for a month, and as many weekly backups as your backup disk will hold.
When I lost a hard disk last year, and all of my data with it, I decided I wouldn't be in that position again. I bought a second hard disk for the machine, and set it up as a mirrored drive so there would be two identical copies. The new machine was ordered with a second drive for the same purpose. I just undid that, and set up Time Machine instead. It won't be up-to-the-minute accurate, but it will also save me from the "oops, I deleted the wrong file" kinds of problems, and that's more important.
If you have a Mac, you need Leopard, and you need to set up Time Machine. Now. Before you do anything else. If you don't have a Mac, get one.