I try to do this as much as I can.
Yesterday morning a tired looking woman at the bus stop asked me if I could read when her bus was coming. I was actually waiting for a taxi to the same place (Easy to just tell the cab driver you are in whatever bus stop, gives you a place to sit while you wait) and her bus wasnt coming for half an hour. So when my taxi arrived I told her to hop in coz I was going to the same place- she tried to help pay for the ride but I said, nah, it would have cost me the same whether I let you come too or not.
She was thrilled, and we had a nice chat on the ride, and it made me feel good.

It wasn’t really all altruistic, though- I LOVE it when people do unexpected things for me too!