Matt Cutts points out a great mashup for apartment hunters: Walk Score. One of the most important criteria I have when looking for a place to live is whether I can walk to (or stumble back from) places. Walk Score provides an easy way to answer that question. You specify an address and it calculates a walkability score. The score takes into account things like the proximity of grocery stores, restaurants and bars.
More than that, it also auto-generates a great little neighborhood guide. Most local search tools require you to search for a business name or category. Walk Score makes it easy to get a feel for a neighborhood by showing the nearest bars, restaurants, grocery stores, movie theaters, libraries and schools.
Here’s a Walk Score map of my neighborhood:
Walk Score doesnt’ take into account hills, so those looking for housing in San Francisco may want to consult a topographic map.
Rakesh Agrawal's blog 
I believe that walk score is cool, but nowadays more and more people prefer to drive cars. Homes are often located in an area where some establishments are easier to get to by car than on foot. I’ve recently found a type of service on drivescore.fizber.com which is called Drive Score. It shows a map of what establishments are in your neighborhood and calculates a Drive Score based on the number of places within a convenient driving distance.
I think that we need to take both into consideration – walkscore and drivecore. It will show the whole picture…