Dialogflow - Conversational UX Platform. (ex API.ai)
Wit.ai - Easily create text or voice based bots that humans can chat with on their preferred messaging...
Microsoft Bot Framework - Framework to build and connect intelligent bots.
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
rasa NLU - A set of high level APIs for building your own language parser
Cognigy.AI - Conversational AI across the organization - service, operations, marketing, sales and HR.