Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.
Kahoot! - Kahoot! makes it easy to create, play and share fun learning games in minutes—for any subject, in any language, on any device.
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
Sli.do - Slido is the ultimate Q&A and polling platform for live and virtual meetings and events. It offers interactive Q&A, live polls and insights about your audience.
Notifu - Notifu, a free open source pop-up balloon utility
Mentimeter - a web-based polling tool for workshops, conferences & events