I am interested in viral marketing stories. What products have being
commertialized successfully using this technique? What have been the
results? How much did the cos. spent in these campaigns? How did they
organized and executed these campaigns?

Almost by definition, viral marketing costs very little, because the
idea is for the marketing to spread itself once released. The classic
example of this is Hotmail in the late 90s. Hotmail appended a
footnote to all emails sent from Hotmail accounts that said "Get your
free, unlimited email addresses at Hotmail.com". As emails were
forwarded and replied to, this text travelled with the message,
exposing lots of non-Hotmail email users to the advertisment.

A close cousin of viral marketing is guerilla marketing, which is
basically trying to disguise your marketing as something else. When
camera phones first came out, manufacturers paid undercover spokesmen
to go to tourist attractions and ask tourists to use the spokesmen's
camera phones to take photos of the spokesmen. The idea was to get the
camera phones into tourists' hands so they could try out the product
without the tourists ever realizing what was really going on.

For a more involved guerilla marketing program, Microsoft used
http://www.ilovebees.com/ leading up to release of Halo2. The campaign
was very complicated and involved, but
http://www.thedailypage.com/features/games/review.php?intgamerevid=2
gives a brief summary.