Mutify - Use a shortcut on any Mac device to mute your microphone
MuteMyMic - Provides a status bar icon for setting microphone input level, and hotkeys to mute/unmute.
MuteTab - Better tab muting in Chrome
AHK MicMute - Control your microphone using keyboard shortcuts
Smart Tab Mute - Ensures that only one tab is playing sound at the same time
Talk Toggle - Mute your microphone with a customizable shortcut.