Beginning today on WordPress.com, users who opt for our Business upgrade will be able to incorporate eCommerce shopping carts into their WordPress.com websites. You can choose between Ecwid, Shopify and ShopLocket. Each option will require you to set up an account with the associated service.
Read our official announcement at WordPress.com News.
For each option, we also provide extra documentation to get you started. For more information, see our support documentation for Ecwid; Shopify; and ShopLocket. Each support page explains how to connect the services to your site and customize them to fit in with your site's look and feel.