National Renewable Energy Laboratory: http://www.nrel.gov/

Sandia National Laboratory:  http://photovoltaics.sandia.gov/main.html

American Solar Energy Society:  http://www.ases.org/

International Solar Energy Society:  http://www.ises.org/ises.nsf?Open

Solar Buzz:  http://www.solarbuzz.com/

Renewable Energy World:  http://www.renewableenergyworld.com/rea/home