Tragofone - White-label VoIP Softphone with WebRTC and Auto-provisioning
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
YakYak - Desktop client for Google Hangouts
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
PhonerLite - PhonerLite enables your PC to use it for internet telephony (VoIP , Voice over IP, SIP).
Slack - A messaging app for teams who see through the Earth!