I'm happy to announce the availability of version 0.6.0 of my camera-control library for 3D sketches, PeasyCam ("P" for Processing, "Peasy" for easy-peasy).

 http://mrfeinberg.com/peasycam/

This version introduces a brace of methods, courtesy of A.W. Martin, which make it easy-peasy to maintain a heads-up display, or HUD. In your draw() method, simply call cam.beginHUD() and cam.endHUD() around anything you'd like draw relative to the camera's position and orientation.

Development is hosted at GitHub:

 http://github.com/jdf/peasycam/

Code:

PeasyCam camera;

void setup() {
    camera = new PeasyCam(this, 0, 0, 0, 50);
} 

That's it. Now a mouse left-drag will rotate the camera around the subject, a right drag will zoom in and out, and a middle-drag (command-left-drag on mac) will pan. A double-click restores the camera to its original position.

It is free for all uses, per the Apache 2.0 license. Please try it out, and let me know how it goes for you.