I keep finding good science demonstrations on the web. Here is Robert Krampf, a science educator from Florida who has done touring show for 30 years. The videos are very professional looking and the demonstrations cover a range of interesting topics. The one that I have embedded here is currently making the rounds on popular sites like BoingBoing and Digg. Krampf's website includes these videos and information about booking his shows. The videos are also available at sclipo.com, another interesting site for sharing knowledge through video.