The Irrlicht Engine is an open source high performance realtime 3D engine written and usable in C++. It is completely cross-platform, using D3D, OpenGL and its own software renderers.
MIDI and/or Custom WAV Metronome for Windows and Windows Mobile
Free open source GPL metronome (a "branch" of "Weird Metronome") for Windows, Windows Mobile, & Pocket PC. Uses user-definable multi-voice WAV or MIDI (PC only) sounds for the beats. Has a blinker & allows user defined bpm & fine measure control.