I'm updating earlier comments in case someone comes across this string.
People are fond of saying Boulder is "different" referring to some of the headlines the town captures in the national press. In the case of housing, Boulder has had a steady growing market over the years owing to a slow growth policy.
From a recent Bloomberg piece: Look at the smaller metros where housing bubbles never took shape, and you'll find some of today's strongest markets.
Other factors are stable employment. Though Boulder has a strong high tech, aerospace and entrepreneurial presence (which historically have been more volatile than other industries), these employers are complemented by government agencies, which include the National Oceanic and Atmospheric Administration, National Center for Atmospheric Research and others. Combined with the University of Colorado, the city can boast a strong employment base that has attracted a highly educated work force.
Check the June 14, 2010 Denver Business Journal and you'll find the Denver metro area leading the rest of the nation in price appreciation. Million-dollar home sales skyrocketed in recent data reported by the journal.
You could probably say Boulder is the strongest of the metro area small communities. But, I would put an asterisk next to Fort Collins, Broomfield and maybe Boulder County as a whole. Credit the energy companies and a few others.
Hope that helps.