Here are some of the sites I've visited, but there are several more that appear after doing a Google Search for "metal business cards".
http://www.plasmaplasticcards.com/me...inesscards.htm
http://www.metalcards.com/
http://www.nexcards.com/
http://www.mcloonebusinesscards.com/
http://www.fenclwebdesign.com/metal-cards.htm
I was most impressed with Plasma Plastic Cards, but some of the other places look pretty good too.