OpenElectrons.com, who have previously created Arduino shields for NXT motors and other NXT bits, have launched a Kickstarter project for a nifty pan-and-tilt mechanism for the camera module called the Pi-Pan. You can still back it for the next 12 days and the mechanism costs $70 delivered. (This is a little bit pricey at first glance, but it comes with a Pi case, all the mountings, the servos and the GPIO controller board so it’s not that bad).
I’ve tried building a pan-tilt mechanism before but found it a bit restricted in terms of the movement. This Kickstarter project seems much better.