Apple TV, Steve Jobs' lonely middle child (~ 200,000 units sold last quarter), came home from school with big news today. Some altruistic hackers had pulled it aside and rejiggered its software to let it support an external USB drive, giving the underwhelming machine something to crow about -- now you can add extra capacity without opening up the case.
Not to say it's simple. Apple maintains that the TV device's USB plug is for diagnostic purposes only; hackers had to do some deft work to repurpose it. In order to use it yourself, you've got to have some skills and special equipment: among other things an Intel Mac; a copy of the Tiger OS; and an Apple TV on which you've previously enabled SSH support. (If you have to ask....)
If you still want to do it, follow the instructions here.