symmetric board edge connector?

Hi guys a couple of questions about hw parts that I'll bet you DIY guys may have experience with.

I'm trying to make a small Arduino clone and am looking for the cheapest way to connect two boards edge-to-edge using a symmetric connector.

A simple example would be to use 2 female right angle connectors and then put (floating) extra long male pins between them. But when I price that out its .50 for each female RA connector and then there are the male pins.

But perhaps you guys know of something even simpler. Perhaps there is a card-edge solution?

And on another subject, I want to be able to use an ATX (PC) power supply to power a board, but I really don't need THAT much power. So I settled on the hard-disk connector as the perfect solution. But everyone just calls it the "molex 4 pin". I can't figure out what the male side (to mount on the board) is really called so I can buy some! Anyone every buy some of these?