Teem - Cloud-based meeting room booking system
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
AgilQuest - AgilQuest is a powerful workspace and meeting room booking software that delivers organizations with a central platform from which to find and reserve conference rooms.
Zulip - Chat for distributed teams. Zulip combines the immediacy of real-time chat with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones.
BOOKMEETINGROOM.COM - Book Meeting Room - Conference & Meeting Rooms Management
WowApp - Wowapp is the best alternative to Skype and you will get paid to use it!