Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Cocorico - Cocorico is a state-of-the art Open Source solution to create an Airbnb or Blablacar for anything.
FB Nearby Friends - Discover which Facebook friends are nearby or on the go
MarketplaceKit - MarketplaceKit is a platform for building different types of online marketplaces.
Facebook Local - Discover places to go and events happening near you
Sharetribe - Build your online marketplace business. You don't need a developer.