My kids are a little young for volunteering (ages 1 and 3), but it doesn't mean they're too young to start learning about generosity and caring about others who are not as fortunate.
This Christmas, I gave them money to put in the Salvation Army buckets whenever we saw anyone collecting, and I let my three year old pick out some of the items for members of the family my department at work adopted in our adopt-a-family program. She really enjoyed that and is still talking the experience.
Edited January 20 2010 by ChicagoMom