Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
SendBird - SendBird is messaging-as-a-service.
Platforma - Wireframe library of layouts and UI elements
Chat by Stream - Build and ship in app messaging in a few hours
Craftwork - A collection of User Interface resources made by Craftwork
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.