I don't personally know anyone who has used their services, but they are featured on the Pachamama Alliance website and wow! their mission is SOOO admirable!!
The mission of Grassroots.org is to serve as a catalyst for positive social change by leveraging modern technologies and business best practices.
Our ultimate goal is to adopt 10,000 nonprofit members, and to provide them each with an average of $10,000 of services per year at no charge (for a total savings of $100 million per year!).
If you've worked with them, please let us know how it went!