Database of State Incentives for Renewables & Efficiency - Information on state, local, utility, and federal tax incentives that promote renewable energy and energy efficiency

NC Sustainable Energy Association - NC non-profit with information on state and federal tax credits

Tax Incentives Assistance Project - Sponsored by a coalition of public interest non-profit groups and goverment agencies, it's designed to give the latest information on federal income tax incentives for energy efficiency with buildings and vehicles