In our agency all communication is done through Slack (and occasionally email). We don't have telephones, all calls are filtered through accounts and reception which is less disruptive.

Everybody has open dialogue about all projects for all clients - each client has it's own channel. It's easy to get up to speed on a project. There are channels for casual chat and a channel to share things through social media which runs through buffer.

Personally, I am also connected to the UX Community slack channels so I can see what's happening in the UK (and around the world).

As different systems are used and proved successful other systems are closed down so we are all using the same tech.

Jessica Hische has one at the bottom of her home page 'About the Site' http://jessicahische.is/