Hubot - Hubot is a standardized way to share scripts between everyone's robots.
Dialogflow - Conversational UX Platform. (ex API.ai)
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Api.ai - Api.
Botpress - Open-source platform for developers to build high-quality digital assistants
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.