Sharetribe - Build your online marketplace business. You don't need a developer.
Cocorico - Cocorico is a state-of-the art Open Source solution to create an Airbnb or Blablacar for anything.
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.
Tangram.co - A powerful no-code marketplace builder. Launch a custom online marketplace for 100x cheaper and faster than hiring a traditional developer.
JaJuMa-Market - All-In-One Multi-Vendor / Online Marketplace Solution. Various Business Models supported.
JungleWorks Yelo - JungleWorks Yelo is software that helps you create a multi-vendor marketplace for your eCommerce business.