From US’s National Weather Service – big precipitation anomalies in US this past year.  The purple areas are extra wet, while the red areas are extra dry.

Precipitation anomalies in USA for 2011 in mm

update:

“Normal” precipitation is derived from PRISM climate data, created at Oregon State University. The PRISM gridded climate maps are considered the most detailed, highest-quality spatial climate datasets currently available. The 30 year PRISM normal from 1971-2000 is used for precipitation analysis since 2004. Prior to 2004 the 30 year PRISM normal from 1961-1990 is used.” from http://water.weather.gov/precip/about.php