Papermind - Papermind Slack App is a collaborative article-editing and document management platform for Slack
Twilio - Brings voice and messaging to your web and mobile applications.
Slenke - Project management & team collaboration
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Trainual + Slack Integration - Capture knowledge or access training right inside Slack
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates