Electron App Store - There are many app stores available for many platforms.
Oberlo - A dropshipping marketplace for entrepreneurs
Secrets of the App Store - Maximize your presence on the App Store.
Shopify - Shopify is a powerful ecommerce platform that includes everything you need to create an online store and sell online. Try it free for 14 days.
Shopify App Store - The most powerful ecommerce app store
WooCommerce - A freely available eCommerce plugin that enables shop facilities on your WordPress website. Functionality enabling extensions & beautiful themes available.