How about using the NAR report?
THIS NAR report:
http://www.realtor.org/press_room/news_releases/2006/ehs_oct06_existing_home_sales_stabilizing.html
shows a median existing home price of $221,000 and an existing median existing condo price of $214,300, each at the end of October, 2006.
If you accept those prices as the "starting points" to be compared with analogous prices at the end of March 2007, we have a "deal".