It seems that more and more specialized websites appear that list videos from sites such as Youtube and Google Video. At the beginning websites that would post lists of tv shows and movies were the most common ones and they are still very popular. Other websites emerge now that only list anime, sports or music videos.
One sector that was a bit neglected until now is documentaries. Best Online Documentaries is a website that tries to change that. They offer nearly 650 documentaries embedded on their website that are hosted on servers like Google Video or Youtube. Viewers can watch the documentaries online on their website.
Several categories like Biographies, History, Science and Mystery and numerous subcategories make it easy to find what you are interested in. All the videos that I tested worked and have a playing time of 40+ minutes. The language is English. Below is one of the videos that you can find on the website. You could really spend several days there.
Update: The website is no longer available and we have removed links pointing to it from the article. We do have a couple of alternatives for you that you can visit instead for a list of documentary related videos.
Watch Documentary lists categories on the left side that you can click on to see a list of videos filed into those categories. A click on a category such as military, history or religious opens a list of videos that are available. The site offers a large list of documentaries that you can watch right on it. Most work quite well and the majority seems to be hosted on YouTube. Some may display an error when you try to play them which may mean that they are country-locked or have been removed from the video hosting site.
The second video site that uses a very similar approach to things is Top Documentary Films which you can also make use of to watch full length documentaries on the Internet.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.