Maestro Metronome is a cross-platform metronome application for Linux and Windows. It's very compact and easy to use.
KpGen is a password generator. It has some interesting features, like a random generator based on mouse movement with some strong options. It can also work as a hash calculator, calculating hashes of passwords and phrases.
Qmmp (Qt-based Multimedia Player) is an audio player with a user interface similar to Winamp or Xmms. Alternative user interfaces also are available.
A simple XML editor.
A C++ math template library.