Tom Ward, whose work will appear in The Best of Instructables book we're currently editing, has just posted an awesome new "extreme business card." It uses a matrix of 5x15 0603 LEDs driven by a PIC16F57 MCU. He says you can get the parts cost down to about $5 each in quantity. Not the kind of card you'd give out on street corners, but if you *really* want to impress somebody...
Dot Matrix Business Card
http://blog.makezine.com/archive/2008/08/dot_matrix_business_card.html