The USGS collects a vast amount of data for a variety of purposes. Something very important they do is they monitor stream gages and report on flood hazards. Recently, Ed Schenk of the USGS setup a camera to gather images of a stream during Hurricane Lee. The animated video, part of a larger project, reveals an interesting time lapse photography of streamgage 1645704. USGS flood data is available online and is perfect to include in your map mashups. See more at http://gallery.usgs.gov