The following have been adapted from the Processing 2.0 library reference and from examples at Learning Processing.

list_capture_devices.pde

/** Print out a list of available capture devices
 * @author Mithat Konar
 */
 
import processing.video.*;
 
Capture cam;
 
void setup() {
  String[] cameras = Capture.list();
 
  if (cameras.length == 0) {
    println("There are no cameras available for capture.");
    exit();
  } 
  else {
    println("Available cameras:");
    for (int i = 0; i < cameras.length; i++) {
      println("camera " + i + ": " + cameras[i]);
    }
  }
}