MarketplaceKit - MarketplaceKit is a platform for building different types of online marketplaces.
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Sharetribe - Build your online marketplace business. You don't need a developer.
Blurtit - Blurtit is a Q&A website. You can ask a question or answer on any question.
JaJuMa-Market - All-In-One Multi-Vendor / Online Marketplace Solution. Various Business Models supported.
Ask Me Help Desk - Ask Me Help Desk is a question-and-answer site.