Many people spend their entire careers in a corporate environment and would never consider seeking a job in a non-profit organization . Some of the best jobs I have had have been in non-profits and I would highly recommend anyone considering a job change to explore them.
If you want to support a cause you believe in and make a difference in the world, look for a job in an organization whose mission you are passionate about.
Do you feel strongly about the environment? Literacy? Healthcare? Politics? Children?
Whatever your interest , you can find an organization that is working to support that cause. Since a public benefit organization exists to fulfill its mission, not to make profits for shareholders, the incentives and atmosphere are totally different. It can be extremely rewarding and personally satisfying to know that your efforts are making an impact rather than just contributing to the bottom line.
See my resources page for more information about the non-profit/public benefit sector.