While the For Sale signs in your neighborhood might not be popping up like weeds, it's a good bet more of them are around—and they’re probably remaining up longer than they used to.

The latest numbers from the National Association of Realtors indicate that the supply of existing homes for sale has climbed to 8.9 months, up from 8.4 months in April 2007 and 6.5 months in May 2006—almost a 37 percent surge in 12 months. Nationwide, there are 4.43 million existing homes for sale, including single-family houses, townhouses, condos, and coops.

The NAR reports that the seasonally adjusted annual sales rate of existing homes was 5.99 million units in May, down 0.3 percent from 6.01 million in April. But the drop from a year earlier was more significant, when the annualized rate was 6.68 million homes. The rate is at its lowest point since June 2003.

“I think psychological factors are currently the biggest drag on the housing market, in addition to a disruption from tighter credit for subprime borrowers,” said Lawrence Yun, a senior economist at the NAR.

Certain factors would seem to point to stronger housing sales. The cost of homes is declining—the national median price in May was $223,700 in May, 2.1 percent below the $228,500 price in May 2006. What’s more, interest rates are not significantly higher than they were a year earlier, according to Freddie Mac: The national average commitment rate for a 30-year, conventional, fixed-rate mortgage was 6.74 percent in mid-June, up from 6.63 percent in June 2006.

But, said Yun, “The market is underperforming when you consider positive fundamentals such as the strength in job creation, economic growth, favorable mortgage interest rates, and flat home prices. It appears some buyers are simply waiting for more signs of stability before they get serious about getting into the market.”—Steven H. Saltzman

Essential information: Read “How to sell your home in a down market” for some ways to increase the odds that you'll find a buyer for you house.