Google Maps Meets Craigslist
In my mind this little utility is simply just a genius mix. The cross pollination of two of the best resources available on the internet-- Google's new mapping service, and the classified listings page, Craigslist. This utility lets you surf both at once-- you can select city, price range, and drag along a map while seeing icons representing apartments for rent or sale. It shows you which listings have pictures, and which don't--and even gives little thumbnails of the property. Make sure to use Firefox if you're on a Mac, Safari is a little weird with it.