Solar Energy Calculator
This Google Map from the UC San Diego allows you to calculate the monthly and annual solar energy impinging upon a 1 m2 tilted plane in San Diego. At the moment the map only works for San Diego addresses but support for additional regions will be available soon.
To work out the solar energy of an area just click on the desired location on the map and enter the panel tilt and panel azimuth into the form. The map will then calculate solar energy incident per square meter at that location and show the results for each month.