Apple Thoughts: A Case for Your iPhone and Your ID

"You know the dilemma. You're going out to the club with your friends and you don't want to take your bulky wallet and your iPhone, but you need them both. The ID Credit Card case from Case-Mate has got your back! The ID case allows you to bring both your ID and your credit card in one convenient iPhone case."

Cool idea, even if it only holds one or two cards. You can find out more at Case-Mate. Another option is this case from Sena.