A few months ago I read an ad in MacWorld about some sort of external firewire device that was essentially an external firewire hard drive, without the hard drive. and you could pop your own 3.5" hard drive in it, plug it into the computer and use it as an external firewire hard drive. I believe they were selling for about 30$. Does anyone know what these are called, where i can find them, or anything else about them? thanks