A recent article in the Wall Street Journal (12/2/08) by James R. Hagerty summarizes that Americans still see real estate as their best shot at wealth. Economists and other pros generally say home prices won't bottom out before the second half of 2009, and some don't see a bottom until 2011 or 2012. Even when they stop falling, prices may scape along the bottom of the run for years.
Over the next 10 to 20 years, housing economists expect prices will rise again--but on average probably not nearly as much as they've averaged over the past decade. You should generally expect house prices to rise just a bit more than inflation and roughly in line with household income.
In the long term, house prices are driven by fundamentals that are hard to predict; immigration, birth rates, the size and nature of households, and incomes. The trick is to figure out where job and income growth will be strongest and where immigrants and others will want to live.