I recently read about the Periodic Table of Videos (I can't recall the blog or source where I read it so I apologize for not giving proper credit) and it prompted me to go back to my Furl Archive and search through for other science related video sites. I found a few more and thought I would share them all in one post.
Periodic Table of Elements
This site is maintained by the University of Nottingham and contains a great collection of short videos that describe each of the periodic elements. The layout of the site is very clever allowing users to click on any element they want to watch the associated video. The content and vocabulary of the videos are suitable for middle school and high school. These videos are hosted on YouTube so there may be filter issues when trying to watch these at your school.
ScienceHack is a collection of science related videos categorized by various topics. These videos are pulled from different sites across the net and not produced by ScienceHack. They claim to review each video before it is included in their database to insure that the content is scientifically accurate.
TestToob is focused on showcasing student created videos that are scientific in content. They have different contests that students can enter with their own videos and each video that is uploaded to the site is reviewed before going live. It seems like the site is interested in promoting science and video production in equal parts. You have to become a member, which is free, in order to view, post and comment on videos.
If you teach science, or are just interested in getting some ideas for different kinds of videos your students could produce, you may find these sites helpful.