Give each person in your class a quarter. Tell them that they can use the quarter for themselves or place it in the jar where the jar will go to a good cause (food shelter, ophanage, etc.). Then leave the jar in the class for a week, and challenge others to help others and to give to the needy.
(This collection could run over a series of weeks for a Sunday School, Mutual, YW/YM, RS, or Seminary class. I especially like to invite my students to _earn_ money to donate to those less fortunate than they are. ~Jenny)