Voice Communications

Aculab - Telephony platforms - cloud, hardware and software.

Asterix - Open source framework for building communications applications. (F)

Grasshopper - Cloud phone system

Line2 -  is a cloud phone service that adds a second line to your mobile phones, tablets and computers with the simplicity of an app

NetFortris - Cloud based VoIP Phone Systems, On-Premise Phone Systems, Collaboration Tools & Contact Center Solutions

Ring Central - Cloud based PBX

Skype - A freemium voice-over-IP service and instant messaging client (F)

Twilio - APIs for Voice, VoIP and Text across office locations and devices