Google has put together a whole bunch of data and imagery from the Mississippi floods on Google Maps.
On Google's Lat Long Blog, Pete Giencke of the Google Crisis Response Team writes:
Emerging as one of the worst flooding events along the U.S. waterway in the past century, the Mississippi River floods of April and May 2011 have caused widespread destruction along the 2,300 mile river system. Historically high water levels from heavy rains and springtime snowmelt have provided no shortage of dramatic scenes -- levees breached, downtown areas completely submerged, spillways opened, and more.
The Google Crisis Response team has assembled a collection of flood data including satellite imagery for impacted cities along the river from GeoEye, flood extent and crest data forecasts from the US Army Corps of Engineers (kml) and NOAA’s National Weather Service (kml), and shelter locations from the American Red Cross (kml).
The image at the top is Morganza, Louisiana on May 15. The following image is from Cairo, Illinois on May 8.
Google Crisis Response is a project of Google.org, the company's philanthropic arm. Its stated goal is to make critical info more accessible around natural disasters and humanitarian crises. Just this year it has provided data and resources for the earthquake/tsunami in Japan, the Christchurch earthquake, the Brazil floods and landslides, and Australian floods.
Last year, it provided resources for the Pakistan floods, gulf oil spill, Qinghai earthquake, Chile earthquake, and Haiti earthquake. In 2009 it provided resources for Typhoon Morakot, the Lockheed Wildfire in Santa Cruz, the L'Aquila Earthquake, and Red River Floods.
To see all available data for the Mississippi floods, simply search for "Mississippi flooding" on Google Maps. The data is also accessible in Google Earth via the "places" layer.