Seriously, why use the lame ass cards we all use? Why not spice things up with unique ways for your clients to remember who you are, what your company does, etc. When going to a business conference bring something that will help you stand out from the rest.
Why not follow in Lego's footsteps?
http://gadgets.boingboing.net/2009/03/27/welcome-to-lego-thes.html
Or you might consider:
http://creativebits.org/cool_business_card_designs