DataPlace

I just made a couple of maps on the DataPlace.com webpage, and am pretty impressed with the vast amount of free information! They have a wealth of demographic info that can be shown on a map or on a chart, including: mortgage values, high income mortgage applicants by race, types of loans, rental attributes, income and employment, and building permits - to name just a few.

The interface is very similar to that of Google Maps. It is a bit more clumsy, but is easy to navigate and refreshes quickly.

If you are looking to do a free market analysis, this is your site.