Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Twoodo - Help your team organize itself using simple #hashtags. Light as a feather. Easy to use. Highly efficient.
Slack - A messaging app for teams who see through the Earth!
Cisco Jabber - Cisco Jabber lets you access presence, instant messaging (IM), voice, video, voice messaging, desktop sharing, and conferencing.
dapulse - Lead by showing your team the Big Picture. Get everyone working together on what's important.
Flowdock - Chat & inbox for teams. One place to talk and stay up-to-date.