I just noticed this RoofRay mashup that uses Google Maps and various other information to help you calculate the solar potential of your building. It’s pretty interesting, actually. You can find your building, trace the potential solar roof area, adjust the calculations based on your estimate of orientation and angle, and then see what you have. After that, you start entering in your electricity usage information and the company you purchase electricity from (watch out though because they didn’t have Rocky Mountain Power’s information and may not have your information yet). After that, you cruise along where they start to provide you with an estimate of the system’s cost, rebates, and potential savings, etc.
All in all, it’s a pretty handy mashup. It’ll help you get an estimate, but don’t shirk your research. You’ll need to do further exploration and verify the numbers, but it’s a great starting point.