Rogue Amoeba just announced the release of version 1.2 of their SoundSource menubar utility. They say that it "has been recoded from the ground up for better performance, and now also features an option to open the Audio MIDI Setup application." SoundSource sits in your menubar and allows you to easily change "your audio input and output sources with a single click" instead of going through the Sound Preference Pane in your System Preferences. If you have to switch sources on a regular basis (e.g. between different microphones, line-in sources, etc. while audio editing or podcasting) then this can be a really handy tool. Frankly the screenshot (right) is not terribly exciting on my machine since I don't have multiple sources to choose from, but nonetheless, you get the idea.
SoundSource a free download from Rogue Amoeba's Freebies Page.