It appears that two of us were working on your question at the same time! In addition to Jim's suggestions, let me add these.

For state incentives:
"The Database of State Incentives for Renewables & Efficiency is an ongoing project of the North Carolina Solar Center and the Interstate Renewable Energy Council (IREC) funded by the U.S. Department of Energy." (from "about us" page) The site has a state by state listing - I can't give you a direct link due to the way the site is designed, but if you select "Search By" from the left-hand list of links, then choose "Incentive Type," you will get a drop-down list where you can select "Personal Tax Incentives," hit the search button, and get the list.

For federal incentives:
The Energy Star program jointly administered by the EPA and DOE has a list of Federal Tax Credits for Energy Efficiency included in the The Energy Policy Act of 2005.

Hope this helps, and feel free to contact us if you need more.