Zendesk Answer Bot - Chatbots
opsdroid - An open source chat bot framework written in python.
Aivo - Skyrocket your Customer Service and Sales KPIs with a Chatbot powered by Artificial Intelligence. Give time back to people.
Errbot - A Python chatbot with a rich and friendly API and an emphasis on developer productivity
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Hubot - Hubot is a standardized way to share scripts between everyone's robots.