Median prices - warren/mar/link
paired houses - ofheo/case-schiller
hybrid - zillow?
http://www.zillow.com/reports/RealEstateMarketChartsAndMaps.htm?msa=United%20States
http://www.zillow.com/reports/RealEstateMarketReports.htm?s_cid=emm-2007111BuzzQ3ReportRePro-bab
http://www.zillow.com/wikipages/Reasons-Why-Median-Sale-Price-is-Flawed?s_cid=emm-2007111BuzzQ3ReportRePro-medianprice