BeatSense - Discover great music hand-picked by real people, in a single click. FREE and in real-time!
EarTrumpet - Volume Control for Windows
20v - Create a custom music channel based on a single song
Sound Control - App-specific volume control
The Midi Shrine - A collection of MIDI files for SNES, NES, GameCube, Game Boy, and others.
Power mixer - Power Mixer is a complete Windows volume control replacement.