CamMotion - a downloadable motion analysis tool for the Mac. From the "VIEW (Video for Exploring the World) project at TERC (Technical Education Research Centers)." Has a demo and manual available online. Has some nice potential but has not been maintained for a while and you may experience some difficulty in getting some of its features to work.
Measurement in Motion - A high quality, affordable, commercially available product for the Mac from the good folks at Learning in Motion. Loaded with features, preview copies can be downloaded for free. Any digital clip in the *.mov format can be analyzed in Measurement in Motion. Points, angles and lengths can be assigned to any object which can then be measured/observed and automatically graphed. The graphs can be overlaid (via drag and drop) with the original clips so students can see the relationship between the clip and the graph of an object. For an example of Measurement in Motion applied to science in sports see Tufts Universities "Slam Dunk Science." For a lesson plan using Learning in Motion see our "Coriolis Force" lesson plan.