Here's a look at the monthly Office of Federal Housing Enterprise Oversight monthly housing price index by US Census Region. The OFHEO index gives us a little different geographic cut than the popular S&P Case-Shiller Housing Index. We can see the extreme fluctuations in the western US, especially in the Pacific states. These are seasonally adjusted numbers current as of October 2008. The black line, depicting the national composite, finishes at 204 - indicating a doubling of housing prices since 1991, but a fall of 8.8% since its peak in April 2007.
The 8.8% national decline is interesting considering the larger declines depicted by the metropolitan focused Case-shiller index.
Judging by these numbers, the housing prices in the 8 states of the West South Central and East South Central Regions appear to be most stable. The Great Plains states fare remarkably well, and the east coast states are falling in line with the national average. Interestingly, end-to-end growth in the Pacific region ends up about the same as the stable south, yet it took a much more turbulent path to reach that point.
According to OFHEO, the data "is obtained by reviewing repeat mortgage transactions on single-family properties whose mortgages have been purchased or securitized by Fannie Mae or Freddie Mac since January 1975." Here's more on the OFHEO housing price index methodology.