Yahoo Local has added a nifty little feature that lets you interact with their maps. Their new dynamic radius circle helps you narrow down the area that you are searching in.
When you're on Yahoo Local, look on the right side of your results for a map. Click “Expand Map.” Then you can drag the circle around, as well as zoom in and out.
The only thing I didn't like is that when you zoom in, the circle stays in proportion to the page instead of expanding or contracting with the zoom on the map.
Here's a screenshot of a search for “coffee” in Washington, DC: