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.
Chirbit - Chirbit is a useful and fun tool that enables you to record, upload and share your voice or audio...
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.
Vocaroo - Vocaroo is a quick and easy way to share voice messages over the interwebs.
WowApp - Wowapp is the best alternative to Skype and you will get paid to use it!
Clyp - Clyp is the easiest way to record, upload and share audio. No account required.