Microsoft® Lync® is an enterprise-ready unified communications platform. With Lync, users can keep track of their contacts’ availability; send an IM; start or join an audio, video, or web conference; or make a phone call—all through a consistent, familiar interface. Lync is built to fully integrate with Microsoft Office. The Microsoft Lync 2010 desktop client is available for Windows and for Mac and mobile versions are available for Windows Phone, iPhone/iPad, and Android devices.
via Business Grade Instant Messaging and Presence – Microsoft Lync.