• Jmyron Webcam Xtra http://webcamxtra.sourceforge.net/download.shtml
• OpenCV http://sourceforge.net/projects/opencv-p5/
• Ess FFT library http://www.tree-axis.com/Ess/ http://processing.org/learning/libraries/audioanalysis.html

Brightness tracking: http://processing.org/learning/libraries/brightnesstracking.html

Webcam example: http://processing.org/learning/examples/webcam.html