Dialogflow - Conversational UX Platform. (ex API.ai)
Meya.ai - Build, train and host sophisticated bots.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Chatbots - Chatbots.org (BETA)
Botpress - Open-source platform for developers to build high-quality digital assistants
Chat Bots Weekly - A weekly curation of everything important in chat bots