PhET: Interactive Simulations
http://phet.colorado.edu/

BBC School Science Clips
http://www.bbc.co.uk/schools/scienceclips/ages/10_11/science_10_11.shtml

NASA Simulations
http://imedia.ksc.nasa.gov/index1.html

ExploreLearning: Gismos (Subscription)
http://www.explorelearning.com/

eduMedia: Interactive Simulations (Subscription)
http://www.edumedia-sciences.com/en/