Airfoil Source Selector is a small application that makes it even easier to connect Rogue Amoeba's Airfoil v2 to different applications:
Line In Camino Firefox iTunes QuickTime Player RealPlayer Safari.
Click the application's icon in Airfoil Source Selector to Get Airfoil to hijack the audio. Click on the Airfoil Source Selector icon in the window to connect/disconnect the Speakers to Airfoil. Note: the audio source applications (e.g. Firefox) need to be installed in your /Applications folder.
If a sound source application cannot be found when Airfoil Source Selector launches, the related icon will be disabled.