Dialogflow - Conversational UX Platform. (ex API.ai)
Gomix - The easiest way to build the app or bot of your dreams
Botpress - Open-source platform for developers to build high-quality digital assistants
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Meya.ai - Build, train and host sophisticated bots.
Motion.ai - Motion is AI based bot builder enabling users to visually build, train and deploy bots to do just about anything.