Tux stickers

[mrkilgoretrout]

The first thing I did after peeling off the "made for M$" sticker on my new ubuntu laptop was to print out a tux logo on sticker paper and put it on over the brand name. We all should do this and get the word out.
http://www.uoregon.edu/~cchapma2/penguin.jpg
Kilgore
http://efemporium.blogspot.com

[magicfab]

I personally prefer these PC case badges:
http://www.thinkgeek.com/homeoffice/stickers/5b43/

[miceagol]

These are nice:
http://www.kde-look.org/content/show.php?content=22435

Print it out on stickers, and stick it on top of the "Designed for Microsoft Windows XP"-logo on your PC.

You find many alternatives on an image search (http://images.google.com/images?q=%22designed%20for%20linux%22&hl=en&hs=2l2&lr=&client=firefox-a&rls=org.mozilla:en-US:official&sa=N&ie=UTF-8&oe=UTF-8&tab=wi) on google.