Jason Snell blogged about Mic Drop, a handy utility that mutes and unmutes your microphone, system-wide, with a global hotkey:

Mic Drop literally does everything I expected from it. It lives in your menu bar and has support for global hotkeys or AppleScript, optional audio and multiple visual notifications of mute status, the ability to choose which mics are muted and which ones aren’t, and even an optional push-to-talk toggle mode.

I don’t do many video calls anymore, but I always hated hunting for the mute key. The visual status in the menu bar and pop-ups are nice touches.