Airportal - Instant customer portals from your Airtable base
Cocorico - Cocorico is a state-of-the art Open Source solution to create an Airbnb or Blablacar for anything.
Airtable Universe - Real workflows from real people
Sharetribe - Build your online marketplace business. You don't need a developer.
Stripe Billing Customer Portal - Stripe-hosted page for customers to manage subscriptions
JaJuMa-Market - All-In-One Multi-Vendor / Online Marketplace Solution. Various Business Models supported.