Microsoft Bot Framework - Framework to build and connect intelligent bots.

Dialogflow - Conversational UX Platform. (ex API.ai)

Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community

Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.

Hubot - Hubot is a standardized way to share scripts between everyone's robots.

Botpress - Open-source platform for developers to build high-quality digital assistants