If you are on a Linux machine and you are lusting after Time Machine functionality on the Mac, there is a pretty good alternative called TimeVault. It doesn't come with all of the cool, some would say unnecessary, graphics that Time Machine does, but it does provide a simple automated way of taking snapshots when files change. Which when you get right down to it is what you really want. It's open-source and free if you are on Linux, it's your best bet for automated back-ups.