Database of State Incentives for Renewables & Efficiency
Lately, I've had frequent occasion to use the Database of State Incentives for Renewables & Efficiency (DSIRE) to search for financial and tax incentives related to energy efficiency and renewable energy. This site from the North Carolina Solar Center and the Interstate Renewable Energy Council (IREC) and funded by the U.S. Department of Energy, provides a "comprehensive source of information on state, local, utility, and federal incentives that promote renewable energy and energy efficiency." It has been updated to reflect incentives in the Recovery Act, and I feel pretty confident in their coverage. There's also a page of links with the major renewable energy, green building, & government sites, and a library of "green" energy policy papers, reports and presentations.