No. 1: Seattle-Bellevue-Everett, Wash.

Average monthly rent: $1,023
Annual drop: -13.8%
Q4 2009 drop: -3.5%

The Seattle area, home to companies that include Microsoft, T-Mobile, and Amazon, saw rent plummet as the unemployment rate rose to 9% (133,300 people) in December, from 6% a year earlier, according to the U.S. Bureau of Labor Statistics. The vacancy rate in 2009 was 6.4%, up from 5% in 2008.