Credit cards have round off corners while most business cards have straight corners, didn't work so well for me as I don't pass them out often, they stay for a while and the corners got bend up.
I use a Muji aluminium card holder: http://www.muji.us/store/...inium-card-case-thin.html Don't carry it every day, though it's small enough that I could. I do keep a couple in my wallet and they seem to stay in ok shape.