Slack - A messaging app for teams who see through the Earth!
Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.
Confluence - Confluence is content collaboration software that changes how modern teams work
Notifu - Notifu, a free open source pop-up balloon utility
Flock - A faster way for your team to communicate
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.