If you're looking for an international ecommerce solution and you're a do-it-yourselfer, you shouldn't have to look further than OpenCart. OpenCart is an open source ecommerce platform that's built on a MVC (Model View Controller) framework, so it's scalable as well.
The platform is full-featured as well: Unlimited Categories, Unlimited Products, Unlimited Manufacturers, Templatable, Multi-Language, Multi-Currency, Product Reviews, Product Ratings, Downloadable Products, Automatic Image Resizing, Multiple Tax Rates, Related Products, Unlimited, Information Pages, Shipping Weight Calculation, Discount Coupon System, Search Engine Optimization (SEO), Module System, Backup & Restore Tools, Printable Invoices, Sales Reports and more…
OpenCart is built using PHP, MySQL, jQuery and CSS… allowing you to fully customize it, theme it, and host it on a standard hosting platform. The site boasts development partners around the globe and a healthy community on oDesk (an outsourcing board for posting opportunities).
Even more notable is a plentiful list of OpenCart extensions. Mobile themes, international shipping costs, language packs, abandoned shopping cart emails… you name it, it's probably already been developed. With 20 major version releases, OpenCart appears to be a great system that's developed for primetime!
Note: I read about OpenCart in .NET Magazine, always amazed at the great resources they find!