Maps are usually implemented as a destination instead of an inline service; Look for the data you're looking for, then get the map of where it is at the end. Some very clever people have hacked Google Maps to get around this pattern of thinking, and in so doing have made the coolest thing I've seen on the web this month, or maybe longer.

Craigslist Housing - Google Maps mash-up. I can only imagine the changes this site will have in the way people think about maps.