I've been fiddling with some data from the National Renewable Energy Laboratory (NREL), and the solar potential in particular has a great spatial angle to it. Using QGIS for analysis, I fused NREL's Direct Normal Irradiance (DNI) database with U.S. Zipcodes. Then I used Developmentseed's Tilemill engine to give a picture of how insolation changes over the course of a normal year. If you click on any of the zipcode polygons, you can tease out the regional variations in specific months, and maybe even make a longshot prediction about how viable it might be to install some rooftop photovoltaic panels.
Sorry, Pittsburgh. It doesn't look good for you or Seattle, honestly. This may not be news to you.