John Battelle characterized aggregate search activity on the Web as a "database of intentions," a treasure trove of data about where people's interests lie.
Google Insights for Search enables you to tap into that database and see how interest in any topic has varied over time, beginning in 2004.
Real estate keyword searches are, I believe, a good proxy for market activity, and a rough indicator of future purchase and rental levels. They're a better indicator than narrative reports from people in the field who are, of necessity, exposed to much smaller populations.
Current search volume paints a bleak picture for Chicago real estate in the near term – volume in November was at an all-time low, an index value of 11 vs the peak value of 100, down 27% from the dismal levels of November 2010.
People's search behavior has become more specific over time with searches for, e.g., Lincoln Park real estate replacing broader search terms such as Chicago real estate. I sampled a dozen popular keyword combinations and all of them were at or near historic lows in November.