RoofRay is a tool that helps you figure out whether it's worth plunking down on money to put solar panels on your roof. If you've long been contemplating going solar to stick it to the man, this tool will give you a fairly rough estimate of how much efficiency you can expect and how it will affect your monthly bills based on past weather conditions, monthly power bills, the slope of your house, and how much paneling you can cram onto your roof.
It does most all of this with the help of Google Maps. It's one of the smarter mashups we've seen, calculating the square footage of your roof based on Google's satellite and aerial imagery. Building the virtual panels is actually the hardest part, as it will do all the numbers-crunching for you--including how long it will take to break even on the paneling, permit fees, installation and upkeep. These are all things that could cost a quarter or more of what you paid for your house.
Short of getting a professional estimate from a solar panel provider this is a pretty straightforward means of seeing if it's worth the investment. However, I'm still a little unsure of its capability to figure out exact efficiencies, or factor in the four hours a day when your neighbor's trees are blocking all that precious bill-paying sun.
Update: If you're interested in giving this a go you should check out Sungevity. Former News.com editor Michael Kanellos covered it back in April, and it does pretty much the same thing as RoofRay with a little more precision due to the inclusion of multiple angles from the aerial photography. It also hooks you up with a proper quote and installation so you don't have to do the legwork when it comes time to get the panels put in.