I've been looking into head-tracking with various sims, and I'm using a homemade IR clip together with Opentrack in the majority of flight sims which support this. However, I couldn't get this to work in CFS3, and I didn't want to invest a huge amount of cost in the official TrackIR.
I couldn't find a great deal of recent activity on this subject, so I thought I'd update this thread with my recent experience.
The solution which worked for me is FaceTrackNoIR together with a cheap MS Lifecam VX-5000.
The software is very cheap - cost me EUR3.45, and I got the camera from an auction site, so overall less than EUR10 for the whole setup and it seems to work well.
Just be aware that you need to make sure you've got decent lighting, otherwise it will not work.
I hope this helps somebody out.