Mattermost - Mattermost is an open source alternative to Slack.
Audible - Audible is the world’s largest provider of premium audiobooks and spoken word content.
Slack - A messaging app for teams who see through the Earth!
LibriVox - free public domain audiobooks
Espresso Chat - Productive conversations start here
LearnOutLoud.com - LearnOutLoud.com is the web's largest resource for audio & video learning.