As I mentioned earlier, my preferred setup for the raspi is to have a very small boot-only halfsize card in the SD slot and a usb hard drive.  To that end, I'm looking for the best USB hard drive for my purposes and I think I may have found it here:

Digital 500GB External USB 2.5" Mini Portable Hard Drive

It's powered by the usb 2.0 port, and uses a mini connector and not a custom connector.  The case is aluminum, which will transfer heat appropriately as well.

The most sensible application here would be to power the raspi and the drive from a nice powered USB hub.  I'll let you know when I find the right one.