I am a big fan of giving back to the community. I think that at some point in everyone's life they should take time and get involved with an organization that they feel is worthwhile. Here are a few that might help you to get started.
National Audubon Society-- This groups helps to raise funds to protect birds and other wildlife.
The Fresh Air Fund: This group helps to take kids out of the city and take them to camp.
American Trees: You can order tree seedlings from this organization, they have hundreds of trees to choose from.
The Breast Cancer Research Foundation is something I really think all women should get involved with, each year 43,500 women will die from breast cancer, this is a disease that if caught early can be stopped, this organization helps to learn about new treatments.