• Amazon - Amazon is one of the web's most trafficked sites and biggest marketplaces.  In addition to selling their own inventory, however, they also allow business owners to sell their own products through the site.  Amazon doesn't charge sellers any per transaction fees, just a $39.95 monthly fee for listing products on the site, with paid upgrades for advertising placements.

• eBay - Known mainly for their online auctions, eBay has actually been increasing the number of fixed-price listings on the site over the past few years.  Small business owners can sell products via an eBay storefront to a huge audience of shoppers.  The site's fee schedule is fairly complicated and includes transaction and insertion fees based on product price.

• Google Shopping - Because results from Google's product search are included in regular Google search results, it's an amazing way for sellers to connect with buyers specifically looking for their products.  The best news for small business owners is that inserting products into the Google Product Search feed is completely free.

• PriceGrabber - PriceGrabber is another oft-used product comparison search engine.  Sellers pay on a cost-per-click basis to have their products listed on the site, which makes it more likely that you'll only pay for solid leads.  For those that don't have an online storefront, PriceGrabber actually offers them to sellers, with automatic insertion in the search engine.

Handmade Goods

• Etsy - Etsy is a marketplace specifically designed for small merchants that sell handmade or locally made goods to reach wider national and international audiences.  The site did $58 million in sales in the first five months of 2009, double what it did in the same period last year.  Sellers pay 3.5% on each sale and a 20 cent listing fee.

• ArtFire - Like Etsy, ArtFire is a marketplace for handmade and local artisan products that has gained popularity because of its liberal pricing model.  Any sellers with less than 12 items listed at a time can sell completely for free -- no listing fees or no transaction fees of any kind. For $12 per month, small business owners can sell unlimited items and gain access to other premium features.

• Supermarket - Focusing on the more artsy side of handmade, Supermarket caters to designers.  The site is curated, so sellers have to apply to get in, but that generally means that buyers are more discerning, and more likely to make a purchase of high quality artistic goods.

Food Items

• Foodzie - Foodzie can be thought of in many respects as Etsy for food (though technically many sellers actually sell food items on Etsy itself).  Foodzie takes a sales commission of 20% of the product price plus a $.60 per transaction fee, which may seem steep, but the site actually does the work of setting up storefronts for sellers and will even take photos of food items at no cost.
  

• Foodoro - Foodoro is similar to Foodzie in that it is an online marketplace for locally produced, artisan food products, but it is more open in its seller policies.  You can set up your store in just a few minutes, rather than having to apply for inclusion, and the site takes a 15% commission on the final sale price of items, without any additional set up, listing, or transaction fees.
  

• Regional Best - Regional Best is like an online farmer's market for artisan food sellers in America.  Once approved, local small business food producers can add their items to the site for sale to an online audience.