I think that in the world of solar, bringing this kind of data into a nation-wide map would be phenomenal to see.

Another possiblity (related to my post on CARMA, yesterday) would be a map showing the relative proportion of solar energy generation by energy utilities, related to total energy generation. We could see it progress over time, and perhaps even show future projections.

I also like the map you did showing “Solar Power Rating”:

http://solar.coolerplanet.com/Content/SolarPowerRating.aspx

I have a suggestion, mainly because I can’t help myself – - but also in the spirit of making this kind of information more engaging and accessible: I think it would be cool if you leveraged the Google maps functionality that allows you to click for details. There’s a table of data under the map of the states, but I think the map would be more engaging if the data from the table were integrated into the map. You could even take it to another level and provide links in the details “speech bubbles” to resources about solar incentives in each state.