I first heard of Net Impact while in business school. The organization attempts to connect folks that want to use business to improve the world. It is composed primarily of folks with advanced degrees and hold full-time jobs in industry.
The New York chapter of Net Impact (full disclosure: I'm on the steering committee) has a blog that's really informative in terms of information related to the relevant sectors and opportunities to get involved.
If you have a college degree and want to use your education to serve the community and connect with folks that want to do the same, I would highly recommend Net Impact.