Cultural Offering has an interesting post on what men should carry. I gave up carrying a wallet years ago, finding it to be a heavy and cumbersome trap for all sorts of junk. Instead, I carry a small leather business card packet for my driver's license, insurance, and membership cards and then a small hard plastic container for credit cards. [I got it from Levenger a while back.]
Cash is in a money clip.
Aside from that:
Swiss Army pen knife
Moleskine notebook (in coat - the notebook also has a pocket for business cards)
Getting rid of the monster wallet was a liberating move.
General rule: Less is more.