Academicearth.org has a wealth of high quality videos, courses, and lectures from several respected universities. There are many science lectures and courses that could be of use to teachers of science. Resources on the site contain a grade so you have an idea of which videos may be more useful. The site was recently voted one of the Top 50 web sites by Time Magazine.
Applications for Science Teachers: High school and AP science teachers could use the science videos embedded in a blog as an extension or homework assignment. Science teachers of all levels could use these video clips for their own professional development in science content.
Other Resources: iTunes U and freesciencelectures.com