As Mariush said, likely if you ground out the green wire, it should start up. Do you have a multimeter and soldering iron? If so, you can build a very basic/cheap dummy load like this:
http://www.k4eaa.com/dummy.htmlYou can then use your meter to check the output from the board.
If they really are dedicated graphics PSU's, as I suspect, I would nab as many as you realistically can.
At the estimated 500w+ output from them, they can definately still find a good use. Hell, if nothing else, you can sell them on ebay as such for at least $50/piece. My PSU for my PC is 750w and I would still enjoy having a dedicated GPU power supply.