PowaySeller:

Hands down the best tool I have seen is this one.

Adjusted Gross Incomes (AGI) from tax returns by zip code

http://www.melissadata.com/lookups/taxzip.asp

You only get 15 free lookups in a day, without messing with cookies or IP addresses.

There are a bunch of other lookups of interest to people with an interest of what is really going on with the RE market.

Happily my AGI is larger than average for my very coastal zip code.

Unhappily, that still means I can't afford a house here, yet.