Is their any hack I can do to save movies to the harddrive or use a usb device to do the same?

Currently there is no way to play movies from the internal hard drive, I'm not sure if it's possible to do so from a USB drive. Maybe someone else can chime in on those.

Only way you can play videos from USB is to buy some 3rd party gadget like this:

http://www.dealextreme.com/details.dx/sku.3814

You would have to control it with its own remote, it could not be controlled by the HU. You'd just plug it into the A/V inputs.