Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Notifu - Notifu, a free open source pop-up balloon utility
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs