Easiest way is to link two Mini DV camera's together with a 4 pin iee1394 cable - play from one and record on the other.

I was looking but couldn't find a program from either Sony, Adaptec or Apple that would do a raw dump either to or from a camcorder to a computer hard drive - that way you could dump from your master tape to your computer, put a fresh tape in your camcorder and dump it back from the computer.

Nevermind - found it - it was apple:
http://developer.apple.com/firewire/

If you have a Mac and lots of disk space you can do it with one camcorder...