RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Empathy - Apps/Empathy - GNOME Wiki!
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Gajim - Full featured and easy to use Jabber client
Phonebooth - Phonebooth is one of the leading voip providers, providing phone systems & phone service for small businesses.
IM+ - Chat everywhere! IM+ is the most widely used mobile IM app! Connect all-in-one to MSN, Yahoo!, Goo...