It's a great simple project with the help of Free Track.
Here are some of the materials your going to need:
a) webcam no more than 320x240, it's not high resolution but will be good enough.
b) for IR Led the recommendation is SFH485P for it's wavelength and viewing angle.
(these items are under a dollar at DigKey)
c) need a resistor try a SFH485P
For more information seek Maximum PC December 2010 magazine