FAB has written an interesting post (see here).
It reminded of a story about a Rabbi, who told his students to take care and realize that ALL men are created in the image of G-d. (Of course the evil people in the world sully that image, but that is not my point.)
One Rabi, riding on a train on a hot day, passed the train's cook-room, and comented to the cook, "You must be so hot today!"
The cook started swearing..."By G-d, you are the only person in _____ years that I have worked here, who thought about the fact that I am HOT!"
So a smile to the postman, newspaper seller, the elevator man, bus driver... whoever you meet today... they deserve a smile and maybe a good word.