Bashupload - Upload files from command line to share between servers
Notifu - Notifu, a free open source pop-up balloon utility
BlackHole File Transfer - Blockchain-based file transfer. Designed for everyday use.
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
FilePizza - Open source application used to transfer file via WebRTC and WebTorrent.
Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.