Mac: If you want to change which mic is being used on your Mac or swap to different speakers, you can always option-click the sound icon on your menu bar and pick whatever you need. If you want more control of those options, SoundSource 3 is the app you want.
SoundSource 3 is essentially that stop option-click menu supercharged. From the menu bar, you can easily adjust volumes, set pass-thru devices and adjust left/right volume independently. If you do a lot of audio recording or engineering on your Mac, SoundSource has long been a necessary tool, and this newest version cleans up the look of it all. You can check out SoundSource for free for a trial run, or if you already own any of developer Rogue Amoeba's other software, like Airfoil or Piezo, you can get a free copy of the app.
Mac only. If you find yourself constantly digging into System Preferences to change your sound settings, free menu bar utility SoundSource sits in your menu bar and allows you to change sources and adjust volume from one unified menu.
SoundSource ($US10 [$13]) [Rogue Amoeba]