One of the hardest parts of tracking large storms is figuring out the damage to the power infrastructure as the storms roll through. You can get a good grasp on how bad a storm is by how much the power goes out, but each power company's outage site is different, and there has been no straightforward multi-state combined view.
The 2011 hurricane season crisis map from Google has the first large scale version of a multi-utility outage map. It renders thematic maps from 5 east coast utilities (ConEdison, Pepco, Progress Energy, Delmarva and Atlantic City) on a single map, pulled from a KML (GeoRSS) file that notes the relative severity of the storms in each area. Map below shows a day with no severe outages, all blue; I'll need to compare with a post-storm power outage.