Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.
Dialogflow - Conversational UX Platform. (ex API.ai)
Rasa Core - Rasa Core is a well-designed dialogue engine used to create chatbots.
Recast.AI - Recast.AI is the leading platform to build, connect and monitor bots.
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.
Gomix - The easiest way to build the app or bot of your dreams