Great write-up on building a quick and dirty PCB business card. It looks like the board can be dropped down to $2 a board. The author uses Dirty PCBs, but the comments section recommended a few others below:
http://www.instructables.com/id/Design-Your-Own-PCB-Business-Card/?ALLSTEPS
http://PCBShopper.com – price compare for a board
http://whxcircuits.com/contact.html for over 50 boards