When I find wallets, I do my best to return them to the owner. In one case that meant riding about ten miles out of my way; I was out for a ride and didn't intend to go that way, but no big deal. Another wallet was clearly way out of my way, so I dropped the whole thing in a USPS mailbox and let someone else deal with it.
I've found several drivers licenses, sometimes with other cards, the detritus of looted wallets. I usually am able to contact the owner and mail them back. The people who get their cards back are always really thankful, offering rewards that I decline, and so on. I always feel funny about this, because the wallet has been stolen and they have no way of knowing that I'm not the one who stole it. But no one has ever suggested I was.
I found a perfectly good cell phone last year. I kept it in my office, charged it periodically, waiting for it to ring. I figured when it rang I'd answer and then I could find its owner by talking to whoever was calling. No one ever called. I eventually gave up, tossed the SIM card and wiped the memory clean, and now use it as a music player or GPS and similar things that I don't want clogging up my actual phone.
Tools and loose cash, those I just pocket. Yes, two crisp $100 bills I found on the street in NYC, and they went straight into my wallet. As I stopped, I was simultaneously thinking "I hope no one is watching" and "I hope the guy who dropped this sees me and flags me down." Well, no one flagged me down, and I kept the cash.
I lost my wallet last week (fell out of my backpack) either on a MUP or right off it. I was hoping someone like you would find it but hours later they were exhausting my transit card. I'm still trying to file a police report to see if the rest of it, less the cash and transit card, makes it to the police. I found out it's basically impossible to file a report on line in Atlanta due to computer "glitches." I guess that's how they can claim crime is going down.