Messenger Video Calls - Facebook Messenger, now with HD video calls
Melrose Labs SMSC Simulator - SMPP SMSC simulator to test SMS messaging applications.
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.
Twilio - Brings voice and messaging to your web and mobile applications.
Voiptime Cloud Call Center - Cloud call center & telemarketing solution
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.