Solar energy
Solar energy technologies include solar photovoltaics, solar heating and concentrated solar power.
General info
Solarserver.de - International web portal for Solar power.
Solarviews.com - Everthing about the Sun and the solar system.
Top50-solar.de - ranking of solar energy websites.
Market and research
Solarscience.msfc.nasa.gov/ - Information related to the Sun, by the Marshall Space Flight Center (NASA).
Solarbuzz.com - SolarBuzz, market studies
solrico.com - Solrico, market studies