A great place to start is the U.S. EPA Environmental Finance Program .
They have published:
A Guidebook of Financial Tools: Paying for Sustainable Environmental Systems. (view HTML)
Or you can download a PDF version.
Catalog of Federal Domestic Assistance. 2000 Edition
A searchable government-wide compendium of all 1,424 Federal programs, projects,
services, and activities that provide assistance or benefits to the American public. It's like a treasure hunt!
- The Foundation Center has a great website full of grants information. You have to pay if you want full access to the Foundations database. However, there is a searchable list of foundations you can browse for free.