This might not be quite the same thing, but there is a man near my home who sells newspapers at the traffic light. He only does it Sat and Sun. I like to give him a bottle of water if I have one with me. When I have the cash, I'll buy a paper and throw in a few extra dollars for him.
As far as beggers go, I typically do not give them money, but one time I did feel the need to dig all the spare change out of my ash tray (it's not used for ashes, just coins) and give it to a man on the corner. Can't explain it really, just felt like I should at that particular moment. Typically I save my spare cash for the man selling papers, though.