Some time ago, I posted a link to Structural Graphics, the people who breathe live into print ads. Here are some more ads that invite people to do something fun with them.
A Starbucks puzzle ad in The Times (ad-rag)
The BMW site in Thailand invites people to download, print out and fold paper models of their cars. Note the Compaq logo on this racer left intact.
An older MINI ad complete with peel-off stickers (library of motoring).