Like probably everybody else, I've been quite lazy taking backups. Through the Linus backup philosophy this hasn't been so bad: my code is in various repositories and my photos are on Flickr. But when a hard drive died on me last year, a bunch of small things were still lost.
Because of this I thought the Time Machine feature of OS X Leopard was quite cool. Until I found out that it would work only with external USB or FireWire disks, that is. I know that if I need to plug something in, I wouldn't do it.
The result is quite cool: while backups take a long time to make, they start automatically when I open the laptop at home. And the Howl setup also makes my N800 Media Player automatically find music from the LinkStation.