Hubot - Hubot is a standardized way to share scripts between everyone's robots.
Messenger Platform - Discovery, chat extensions, and richer experiences
Dialogflow - Conversational UX Platform. (ex API.ai)
Api.ai - Api.
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.