Automuter is an application that stays in system tray notification area (near windows clock). It can mute speakers when computer is locked, when screensaver is running. Alternatively, you can set up you own silent time schedule or mute by hotkey.
IndieVolume allows every application have separate volume/mute level, independent from other applications volume/mute level. It allows per-application selection of playback device. It allows to mute any application when selected applcation is playing
