Sixty symbols Physics
http://www.sixtysymbols.com/

Turn PowerPoints into Podcasts
http://www.powertolearn.com/articles/teaching_with_technology/article.shtml?ID=79

simulations
http://mw.concord.org/modeler/index.html

Tracker which is an open source (read: free) tool that works beautifully:
http://www.cabrillo.edu/~dbrown/tracker/