Buying a car? AutoBaron is an interesting new site that lets you find the best deal using a chart format. It's one of those "got to see to fully understand" type of services, but I'll try to explain briefly.
Say you were shopping for a Mini Cooper. Visit the home page, select the make, model and year. In response, a graph will appear. A line chart shows the average value of the car, value dropping as mileage increases. Any listings are also shown on the chart, scattered around the line as car icons. You can easily spot potential bargains that appear below the value line. Hover over one of the icons, and a picture of the car and some brief details appear. Click, and you'll go right to the online listing.
Downside? It covers only the US -- and all of the US initially, by default. So if you're in California, finding a bargain in Florida isn't that helpful. But you can narrow by zip code, as this chart for the Newport Beach, California area and a radius of 50 miles shows.
Not into graphs? You can also browse listings, as this example shows.