I've been using one of these for about ten years now, it's perfect (for my needs, obviously).

http://www.amazon.com/Dopp-Regatta-Magnetic-Money-Black/dp/B0006M4L3E/

Carries cash, ID, and transit pass on the outside, and the inside fits credit and debit card, insurance card, and one or two other cards as needed. The notch makes it easy to remove cards, and the whole thing still fits comfortably in a front pocket even while sitting down.