Slapping a wifi card into a pc isn't very ground breaking, but [Darkside] had to add a PCI header and trace the board just to hook up a keyboard before he could do much with his old intel vpn gateway. In the end, he added m0n0wall and a wireless card to turn it into a nice wireless router.
http://www.hackaday.com/2007/08/12/old-intel-vpn-to-wireless-router/