Etsy is an online marketplace to sell and buy handmade things,vintage items and so on... There are many categories, including art, photography, clothing, jewelry, books, furnitures, beauty products, toys and many more. Registration not required.
BeamSnap is a "social marketplace" that lets you buy and sell items like you would on eBay.You can post your items and buy from other users, you can actually share what others are selling and be rewarded. That is why the "social" element, the site encourages you to share listings with all the friends and contacts you have on Facebook, Twitter, ecc. If they buy anything you have shared, then you'll get a commission.