Zip Loc bags in any size I have a leather fanny pak from Wilson's leather that is quite water-resistant but we all put our wallets in a small zip loc anyway and it never sees a drop of moisture! DH just puts his in his pocket. we use the sandwich size bags.
We got an aquapac (www.aquapac.net) to put the important stuff in. We have a bigger one for a camera and cell phones and a small one that's just big enough for credit cards, tickets, and some cash. They worked really well and we just put them inside the other bag we were carrying. That's really all we cared about not getting soaked. Anything else we didn't really care of it got wet or not.