Academic Earth (organzation). Free video lectures from major scholars in a variety of disciplines, including the sciences.
Films on Demand (NU only). A collection of streaming videos available to the NU community.
Government Resources for Science Images (Library of Congress) Many free, uncopyrighted images collected from US Government agencies.
Nova (PBS) Streaming access to productions.
Science Nation (National Science Foundation). Vidioes and images from science topics of current interest.
Science Photos in the News (National Geographic Society)
Science Service (Smithsonian) Science images from 100 years of serials publications. Though copyrighted, may be used for academic purposes.
Scitalks (commercial site) 100's of streaming videos in all aspects of science for viewing, but not reproduction.
Videolectures.net (Jozef Stefan Institute). Over 6,000 video lectures, mostly in the sciences. An excellent resource for students, educators, and scholars.
Also, see the Science Podcasts page, as many podcasts also include videos.