We've been remiss in not having written of Oodle before, a relatively new search engine for local classified listings. Oodle scans the web to find listings of items for sale posted on places like Craiglist, newspaper classified pages and eBay, among others. It's not just items for sale, either. You'll also find used car listings, rentals, jobs and other locally oriented services. Expect a longer look in the future. In the meantime, check the site out. It just added listings for Minneapolis/St. Paul and Milwaukee, bringing coverage up to 22 metropolitan areas in the US.
In some cases, you can also view listings on a map. This currently is limited to housing listings, as shown here. To get to these map listings, pick a city from here, then choose the Housing tab and then the "View listings on map" icon at the top of the results that come up. Also watch to see if this option appears for other types of listings, in the future.