Viral video research

Stumbleupon is a great resource for finding things like this - it sends you from site to site all linked by the topic you've chosen to "stumble". The sites tend to be of pretty good quality too.

http://www.stumbleupon.com/su/1DDivI/www.techipedia.com/2010/viral-video-traits/

http://www.stumbleupon.com/su/2Z7BCv/www.ugo.com/the-goods/the-50-awesomest-viral-videos-under-30-seconds-long-1?page=9/

This one specifically shows videos used for marketing campaigns:

http://www.stumbleupon.com/su/24bODL/www.blogstorm.co.uk/the-top-10-viral-marketing-campaigns-of-all-time/

Plenty of these videos are so well known that I haven't posted the videos themselves, these sites reference several more too, but I haven't time to watch all of them!