The cogsci.nl software family has a new member! Mantra is a program for object tracking and has been designed specifically to be used in psychological experiments. For example, with Mantra you can track the hand of a participant while he/ she is performing some kind of experimental task. There are a number of example experiments available, showing how to use Mantra in combination with E-Prime and Python.
Although there are, of course, many object tracking systems available, the beauty of Mantra is that it doesn't require expensive dedicated hardware. You simply plug in a decent webcam and you are good to go!
You can find downloads and more information here!