I just wanted to mention the great Open Source multi-touch tracking application Touché for Mac OS X from Georg Kaindl in my blog.
Touché supports lots of image processing possibilities and is written purely in the Cocoa Objective-C framework from Apple. The Touché code can be accessed via Google Code. Touché supports loads of video cameras amongst others the Pointgrey Firefly MV.
However, Touché seems to be the best choice for everyone, who wants to use Mac OS X for the tracking in multi-touch setups. It is highly cofigurable. Georg Kaindl is developing Touché on his own. Thus, there is only one responsible, friendly and very capable programmer that can be easily contacted.