Slack is a team-based communication and archiving platform. It allows for both synchronous and asynchronous communications, channels for managing specific streams, full user management and integration with a wide variety of social media and storage providers. It is free for limited (rather generous) use and provides one the best means to allow for individual communication patterns within a managed project to be facilitated. Allowing for the quick and informal communications, hashtagged for quick scanning and searching as well as targeted messaging makes it a very compelling project tool. The addition of specific mobile clients with notifications makes it a very effective project management tool.