Funnily enough I found about 40 or 50 quid on the car park opposite the library in Holmfirth last year. I had a bit of a moral dilemma and felt it pointless to take this to the Police Station (if it was even open!) as it's highly unlikely anyone who lost this sort of money would have gone there - I'd certainly never bother going there if I'd lost it.
In the end I donated to the charities around the 50th Anniversary event so I felt it went to a good cause and if the money came from a drugs deal even better