EarTrumpet - Volume Control for Windows
Volume2 - Volume2 is an advanced Windows audio mixer, a complete replacement for the standard Volume Control.
Volwheel - VolWheel is a little application which lets you control the sound volume easily through a tray icon...
3RVX - 3RVX is a skinnable volume display and controller.
Volti - Volti is an GTK+ application for controlling audio volume from system tray/notification area.
Power mixer - Power Mixer is a complete Windows volume control replacement.