KMail
KMail is a free and open source email component of Kontact, an integrated personal information manager from KDE
Minder
Minder is a free and open source software for creating mind maps
ColorMate
ColorMate is a free and open source small app for converting color between three notations #rgb, rgb() and hsl() for Linux
Sylpheed
Sylpheed is a free and open source, multi-platform, simple and lightweight email client
Evolution
Evolution is a free and open source application for managing personal information: mail, contacts, calendar, tasks, and notes
gmusicbrowser
gmusicbrowser is a free and open source software for listening to audio, a music player for large collections
Lollypop
Lollypop is a free and open source music player and music collection organizer
ANoise
ANoise is a free and open source user-friendly app that allows you to play ambient/background noises
MoonPlayer
MoonPlayer is a free and open source video player for playing and downloading online videos from YouTube, Youku, and iQiyi, as well as local videos