I'm happy to announce the availability of version 0.8.0 of my camera-control library for 3D sketches, PeasyCam ("P" for Processing, "Peasy" for easy-peasy).

 http://mrfeinberg.com/peasycam/

Version 0.8.0 adds default mouse-wheel zoom behavior, which can be turned off or customized.

Version 0.7.0 added customizable mouse-drag handlers.

Version 0.6.0 added easy-peasy HUD (heads-up display).

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, mouse wheel or 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.