I like Audio Manager. You can set different profiles. You can put skins on it to better match your theme/wallpaper. You can use either an icon, a widget, or pin the app to your notification bar. The app doesn't normaly look like it does in the screenshot below. It is themed with the Breeze theme that is made for the Ultimate Droid. I like Audio Manager though I will admit that I haven't tried all of the apps that was previously mentioned in the other post yet.