I bought a little homeless guy a happy meal from McDonalds about 2 months ago, you should have seen his face, it made my day. I felt good and at least I know I bought him food and never gave him cash to go buy drugs/drink with.
I'm not by any means a well off person. I work 2 jobs, 6 days a week just to survive but just making a smal gesture like that can really give you and the other person a boost. Everyone should donate something at least once a month to those in need.