Heat maps?

[Joshua S.]

I've been thinking that some real estate heat maps for things like home values would be really useful. My google searching led me to this Trulia map-

http://www.trulia.com/home_prices/

They have the right idea, but it's not detailed enough. It stops at the county level. Does anyone know of something like this that goes further down to the level of individual homes?

And semi-related, does anyone know of any kind of software program that lets you copy/paste or import a list of addresses (like from a spreadsheet) and then shows them as points on a map? I would like to obtain a list of cash transactions in my area and see them all mapped.