Science Friday - Videos on NPR's Talk of the Nation Science Friday's website. There's some good stuff here. The videos are typically related to topics that were covered by Ira and his guests.
Secret Life of Machines - Was a series created in the late 80's to the early 90's. The main premise was to show how modern devices came to be. In order to get there they show everything form how life was prior to the invention and every incarnation of a machine. There is a lot of really good science in these. The only unfortunate bit is that they are a bit dated. So, whenever I show one I talk about advances that have taken place since the video was produced. The videos can be streamed from the net or downloaded in iPod format.
Periodic Table of Videos - This is a great collection of videos. One about each element. The videos are hosted through YouTube, but they have an alternate server if YouTube is blocked for you.
Sixty Symbols - By the same folks who brought us the Periodic Table of Videos we have Sixty Symbols in Physics and Astronomy.
Why is it so? A "best of" from experiments from the series. Great videos!!!
The ground-breaking TV series with the enigmatic Professor Julius Sumner Miller - ran on the ABC from 1963 to 1986. Professor Miller's infectious enthusiasm for physics delighted, educated and entertained generations of Australians, most of whom have at some point asked each other 'Why is it so?' in the characteristic Julius Sumner Miller voice.scitalks.com Great science videos collected from around the net. These come from academic speakers and broadcast TV. Search for topics/speakers of interest or browse by subject or audience type.
The Annenberg/CPB site has a lot of great streaming videos that could be used across the curriculum in just about every subject. The site requires you to register, but registration is free. The list of hosted videos includes some relatively famous educational series (including Mechanical Universe and The World of Chemistry)
The American Field Guide has many great environmental videos that can be used in any life science curriculum. There are also some geology, earth science, and archeology videos available.
The Vega Science Trust hosts videos of lectures, round-table discussions, and workshops that present the cutting edge of science. Some would be appropriate for students while others just provide great education for teachers. The site also has some educational resources to go along with some of the videos.
101Science.com has lots of great links for science videos. Some of the above links came from there. This site hosts a lot of other really good stuff as well, but I haven't had a chance to surf through it all yet.