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 (i.e., video) 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();
  } 
 
  println("Available cameras:");
  for (int i = 0; i < cameras.length; i++) {
    println("camera " + i + ": " + cameras[i]);
  }
}

show_capture_by_parameters.pde

/** Show video using requested capture parameters
 * @author Mithat Konar
 */
 
import processing.video.*;
 
Capture cam;
final int CAM_WIDTH = 320;
final int CAM_HEIGHT = 240;
final int FPS = 15;
 
void setup() {
  size(CAM_WIDTH, CAM_HEIGHT);
 
  if (Capture.list().length == 0) {
    println("There are no cameras available for capture.");
    exit();
  }
 
  // Instantiate a new Capture object, requesting the specs:
  cam = new Capture(this, CAM_WIDTH, CAM_HEIGHT, FPS);
  cam.start();  // In Processing 2.0, you need to start the capture device
}
 
void draw() {
  if (cam.available() == true) {
    cam.read();
  }
  image(cam, 0, 0);
}

Note that Processing will crop the capture to the canvas size if it doesn't fit.

show_capture_by_devnum.pde

/** Show video using specified capture device
 * @author Mithat Konar
 */
 
import processing.video.*;
 
Capture cam;
final int CANVAS_WIDTH = 320;
final int CANVAS_HEIGHT = 240;
final int camnum = 55;  // Pick a camnum that makes sense given the canvas size!
 
void setup() {
  size(CANVAS_WIDTH, CANVAS_HEIGHT);
 
  String[] camera_list = Capture.list();
 
  if (camera_list.length == 0) {
    println("There are no camera_list available for capture.");
    exit();
  } 
 
  println("Available cameras:");
  for (int i = 0; i < camera_list.length; i++) {
    println("camera " + i + ": " + camera_list[i]);
  }
 
  println();
  println("Using camera " + camnum + ", " + camera_list[camnum] + ".");
 
  // Instantiate a Capture object by specifying the device name stored
  // in camera_list array:
  cam = new Capture(this, camera_list[camnum]);
  cam.start();  // In Processing 2.0, you need to start the capture device
}
 
void draw() {
  if (cam.available() == true) {
    cam.read();
  }
  image(cam, 0, 0);
}