OAuth Intro

There are the links of a great and simple intro video to understand OAuth:

 - Part1: http://www.youtube.com/watch?v=LRNg4tDtrkE
 - Part2: http://www.youtube.com/watch?v=2KG05SnAYlE
 - Part3: http://www.youtube.com/watch?v=qPHLsLlQ7Rw
 - Part4: http://www.youtube.com/watch?v=0PvQcLzVGF0

Here is the url with a nice explanation about how auth works:

http://hueniverse.com/oauth/guide/workflow/