Animux comes with a camera tracking software that runs only in the 32Bit/64bit version and not in the PPC version. It does a pretty decent job at it.
For Motion Capture there have been some that we have 2 options that we are investigating ....
1. "Johnny Lee's project type approach with wii remotes " to create a cheap infrared motion capture rig.
2. Camera based motion capture with a lot of image processing (like the computer vision software that have been worked on in linux) . Also with the number of camera drivers for linux increasing, helps in this cause.
Mark
P.S.
You will find these articles of some interest
http://wiimocap.blogspot.com/http://procrastineering.blogspot.com/http://ask.slashdot.org/article.pl?sid=06/08/17/0132246http://www.zoneminder.com/