In keeping with my quest to find more free, online video sources, I have a new one to add to my list: the Smithsonian Channel! Last summer, our family took a summer trip to Washington D.C. that included a whirlwind tour of the top 5 Smithsonian Museums. You could spend weeks there and never see everything that that the Smithsonian has to offer, and this site seems to follow suit.
Videos are divided into categories: Air and Space,Science and Nature, Culture, History, and Kids. You can also view the latest videos, the most viewed, or search the site. These great videos are also available through YouTube and iTunes for easy viewing and for downloading. The only downside I found to this site was that most of the topics I searched for yielded full-length videos, not always a great option for regular classroom use.
Still, Smithsonian Channel is a great resource for high quality, free video viewing!