Some nice petitions I found with Google:
Sign the petition at http://saveie6.com/ and help us save IE6! It was 1 april joke, but it is still alive!
IE6 Must Die - Support Campaign | Twibbon
http://ie8-must-die.com/petition/
http://www.techbeast.net/2011/08/08/petition-to-stop-using-internet-explorer-6/
Sign petition: Change the internet explorer symbol · GoPetition.com
petition: Exterminate Internet Explorer
Petition Online - Petition Online has been retired
Which one did you join?