What you do is you type in an address, or even just a city, then pick the type of map you want to look at, then hit search. You can see the owner-occupancy rates in each neighborhood or zip code, along with other data like median income, median rents, how many families live there, etc.
Plus, it has HMDA data (Home Mortgage Disclosure Act) and you can see what home mortgage activity has been like over a five year span.
Anyway, it seems like a lot of academic types use this site, but I bet it's useful to regular folks, too.