Wow! Seattle Eric alerted me to this new site called Zillow.com that was created by the founder of Expedia. Basically, it's another real estate comp site - but this is much, much better than anything I've seen before! It looks like they've combined comps with Google maps to give you a satellite view of the neighborhood with home values superimposed. Click a house to get details about it. This gets my vote for best use of the Google Maps.
This is still in beta, so there are some bugs. I've noticed that when you zoom in to the highest magnification, you tend to end up somewhere other than where you were looking - I ended up about 5 miles east when I tried it. Also, at higher magnifications, the hybrid view, which superimposes street names onto the satelite view, gets confused and puts streets where they aren't.