I just heard a good piece of advice from a fellow conference participant about something to bring on the trip- a polaroid camera.  I don't know if it will fit in the backpack too well, but I thought it was interesting.

The idea is that you have two cameras- the "good" camera and a polaroid. When you see someone you'd like to take a picture of, it's a good thing to be able to offer the person something- an offering for their time.  As opposed to money, we could take a picture with the good camera and then take a polaroid picture to give the person.   She said that it makes for an awesome gift that is fun and a great way to spread good will.

Now, we just need a lightweight pocket-sized polaroid camera. Thanks for the idea Karen!