Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
Notifu - Notifu, a free open source pop-up balloon utility
Microsoft Teams - Microsoft Teams provides the enterprise-level security, compliance and management features you expect from Office 365, including broad support for compliance standards, and eDiscovery and legal hold for channels, chats, and files.
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
WebEx - Cisco WebEx Web Conferencing, Online Meetings, Desktop Sharing, Video Conferencing
Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.