UTF-8 can encode any Unicode character, preventing the need to set a encoding type for every language that is going to be used in the site and allowing output in multiple languages at the same time. I would recommend to use this type of encoding in case you are setting up a multilingual e-shop on a MySQL5 / PHP5 platform.
osCommerce is a complete e-commerce solution that contains both a catalog frontend and an administration backend. Although osCommerce offers a plain set of commonly used tools and modules, its big online and growing community provided thousands of add-ons, modules and branch specific tools throughout the years.