Leave the wallet where I found it
Take the wallet
Just take the cash, leave the rest
Just take the credit card, leave the rest
Take it to a police station
Try to track down the owner (via adress on the license)
I've been on the finding and losing side a few times. I know what it's like losing a wallet and it's no fun. Regardless, I simply could not live with myself if I took something that did not belong to me. It's that simple. So I would return the wallet to the owner with every dollar intact.
I have a few lost wallet stories, so I'll bore you with one right now. Back in my university days, my wallet was stolen from my purse in a bar. I was irked, but what could I do? So I had to take the painful steps (*ahem* pre-internet days!) to get all of my cards and ID back.
Queue 12 years later, I get a package in the mail. It's the wallet. No money, but the ID is all there (not that I needed it). I had lived at various addresses in all those 12 years, but yet, it found it's way back to me. I have no idea who sent it, but they must have had an interesting time tracking me down. I thought it was very cool, even though I had no more use for it.
"There is a lot of talk coming from CitiGroup about how Dodd-Frank isn't perfect, So let me say this to anyone listening at Citi —I agree with you. Dodd-Frank isn't perfect. It should have broken you into pieces." -- Elizabeth Warren
Mail everything to the address on the license.