Dialogflow - Conversational UX Platform. (ex API.ai)
indemandly - Live chat 2.0: Customer messaging that converts
Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.
Message Me - Website to create your contact business card
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.