http://www.energystar.gov/index.cfm?c=tax_credits.tx_index
Government website providing information on federal tax incentives
http://www.dsireusa.org/
Easy to use site providing information on federal, state and local tax incentives
http://www.irs.gov/newsroom/article/0,,id=204671,00.html
Information on the $8,000 tax credit for first time homebuyers
Solarnomics
With all the variables associated with installing a photovoltaic (PV or solar panel) system on your property, determining the financial benefits of panels can be difficult. We call the study of these financial benefits solarnomics.

The DoE has a great section on the costs/benefits of a residential solar panel system. Also, check out this solar payback calculator for an idea of savings in your area.