Craigslist
craigslist.org
We repeat this previous "50 Coolest" pick because it just keeps getting better—there are separate sites listing ads for bikes, boats, baby gear, musical instruments, jobs, apartments (you name it) in 120 cities in 25 countries. Only certain businesses pay listing fees. LiveDeal.com likewise works to connect buyers and sellers who share a zip code, to facilitate sales of used items that are difficult to ship—or that most people would want to try before buying (furniture, cars)— something you can't do on, say, eBay.