Here's a guide written by the Case Foundation. It explains what impact investing is all about and educates folks in deciding what's right for them, for their families and for their environment. The Case Foundation has a great philosophy:
"We believe the world needs more fearless approaches to social change, so we take risks on new ideas and approaches, and partner across sectors with people and organizations that share our fervor to engage citizens and change the world for the better, today. We don’t limit ourselves to any one sector or issue, but instead let a set of core values drive all of our ventures."