Hubot - Hubot is a standardized way to share scripts between everyone's robots.
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Messenger Platform - Discovery, chat extensions, and richer experiences
Landbot - An intuitive no-code conversational apps builder that combines the benefits of conversational interface with rich UI elements.
Dialogflow - Conversational UX Platform. (ex API.ai)
Botsify - Ever wonder if you could replace your live chat support system with a chatbot?. Its possible now with Botsify Chatbot For Website.