Perhaps the Dummies guide to use Keepvid. Referring to Youtube's Terms of service it does not clearly says but yeah, they don't want you playing around download videos since they are a streaming website. On the other hand, it is itself paradoxical. Because when we are seeing any video, it is being stored on the computer in the form of cache. Pretty much one can't distinguish downloading video from seeing it in the browser. Even though it would be good if you download only legal content, downloading copyrighted things which are itself uploading illegally is still a crime(just like downloading songs from pakistani website or using torrents to download movies) which is not advised.
Open Youtube.com and select your favorite video to play
Now select the URL and copy it. (right click and click copy).
Pretty interesting. A month from now i would be able to derive this time. Thanks to Physics, it is really an awesome thing, with real calculus it comes to life. And the best, all you need to have is Internet.
Academic Earth
Another good domain.Niche for every Lecture out there.
There are certainly more people who are teaching, like PatrickJMT, on the internet, keep trolling. Listen to Richard Feynman, some here & Stragely it is Microsoft, Project Tuva. Then the classic way in which Carl Sagan speaks, plenty of videos on youtube.
Talking about physics as a vocation, there are many more blogs out in the net yet i got specifically amazed by Starts with a Bang (not forgetting to mention, Yes, everytime someone sees the author's picture, 3 children die in Angola. He should change it).Ponderabout.com is also a great place. I don't stick to too many places, it gets real hard to read them everyone. At last Discovery News is a must in your RSS reader. [More Earth: Ten things you don’t know about the Earth]