Best websites for comparing real estate market data? (US)

[Robert Schwenkler]

Hey gang,

What website(s) do you use to look at and compare real estate market data?

Redfin, realtor, etc all obviously have their data... are there other websites any of you use that might be suitable for more data-savvy people who are interested in e.g. cross-market analysis or getting more refined data for individual markets?

Thanks!

[Trevor Richardson]

(NAR) National Association of Realtors has some of the best real estate data that nobody knows about. Their SFR quarterly (ranked) median home sales data is unparalleled. Their source is all MLS data pulling from coast to coast, it's fantastic.