Open Source ASP.NET Shopping Cart: AspxCommerce
AspxCommerce is an open e-commerce system that is built with ASP.NET and uses MSSQL for storing the data.
The application is built on top of SageFrame (the open source CMS) and comes with a single-click installation.
It has an easy-to-use admin panel for creating and managing categories, products, users, orders and the settings provided.
There are various marketing features like the ability to bundle products or discounts based on price/products.
AspxCommerce has different modules that an e-commerce site may need like community poll, customer testimonials, Google Maps store locator, etc.
The layout is themable and multiple themes exists to choose from or you can create your own with ease.
It is SEO-friendly, has a multi-language interface and updated/improved regularly.