Notifu - Notifu, a free open source pop-up balloon utility
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.
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.