What makes a viral video? and a viral sequel?

Good summary article on what makes a viral video with the 10 most viral videos of all times + how they got there. To see Numa Numa again @ Lifebeyondcode

Viral videos

Good overview of the most viral ads with a most personal favorite for Gilette :-)
@AdAge

Recipe for a Successful Viral Video

Creative & marketing folks always want to make videos viral:: nothing new here but a quick overview of what not to miss from the WSJ.com