What would you do if you found some cash?

[ABV]

So I walked up to some cash laying on the ground today in my apartment building. It's more than a couple bucks and less than $100, but still a significant amount. I think I know what I'm going to do with it, but I was just curious to see how other people would realistically handle the situation.

You're walking along and find some cash. You're reasonably sure you know the general population that it came from (like an apartment complex or workplace). What do you do?

At least make an attempt to find the owner
Donate it
Finders keepers
Leave it and let someone else deal with it