Dialogflow - Conversational UX Platform. (ex API.ai)
Typeform - Create beautiful, next-generation online forms with Typeform, the form & survey builder that makes asking questions easy & human on any device. Try it FREE!
Botpress - Open-source platform for developers to build high-quality digital assistants
chatform.ai - Turn your web forms into conversations on any messaging app
Meya.ai - Build, train and host sophisticated bots.
Landbot - An intuitive no-code conversational apps builder that combines the benefits of conversational interface with rich UI elements.