This post originally appeared on the American Express OPEN Forum, where Mashable regularly contributes articles about leveraging social media and technology in small business.

With more than 500 million active users on Facebook, there are more potential customers using Facebook than there are logging into eBay and Amazon combined.

Most of these users don't see the site as a purchasing platform, but more and more businesses are adding an option to use the social networking site to browse and buy their products. These four Facebook apps offer flexible options for adding a storefront to your business page.







Free beta app Payvment allows you to handle your entire e-commerce operation through Facebook. The app allows you to accept credit card and PayPal payments, which are credited to your PayPal account. You can customize charges for shipping and choose whether to charge sales tax.

Unless you disable the option, your products will also appear in searches people make on other Payvment storefronts when they choose to search “all of Facebook.”

Other helpful features include selling multiple quantities of an item from one listing, give discounts to customers who like your page and adding options like sizes or colors to item listings.

Store owners have access to their selling histories and order statuses, and they are able to send messages to buyers through the app. Implementing Payvment’s instant payment notification can help keep on top of orders as they're made.







Storefont Social creates a tab on your business’s Facebook page that allows you to showcase items in your online store. Some templates include options to tweet or share specific items, and shoppers can search by customizable categories or with a search bar. In order to set the store up, you need to install the Storefront Social app. The basic package costs $9.95 per month.

You cannot use the store as your sole storefront because there is no way to complete a transaction using the platform. Rather, people who wish to buy your products are directed to the product URL that you provide.

If you are a seller on eBay or Amazon, you could link to your listings on those sites, as well.







Like Storefront Social, BigCommerce SocialShop doesn’t allow transactions. Rather, it directs users interested in products to an online store — in this case, a BigCommerce online store — and allows them to share their products on their walls.

Because BigCommerce is a full e-commerce platform, it’s a more extensive Facebook storefront tab option. At $24.99 per month for the most basic package, it’s also the most expensive.







E-commerce site builder Ecwid also has a Facebook storefront option, but unlike BigCommerce SocialShop, the app allows customers to drag and drop products into a shopping bag and check out without leaving Facebook. You can integrate the same store on your website, MySpace profile, LinkedIn profile, or Tumblr by copying and pasting a widget code.

Basic accounts are free, but selling more than 100 items will cost you $17 per month.

Image courtesy of iStockphoto, thesuperph