With AR in mind (see last post) I saw this on Mashable and I think it is a great example of AR used in promotional marketing.

When you hold up a promotional pack of Doritos (in Brazil) to the webcam, the AR code printed there then initiates a little cartoon character which is active within the Orkut community. Orkut is big in Brazil (bigger than Facebook or Mypsace I think, so that makes sense as a platform for extending the campaign).
And with lots of different AR codes on packs, I assume that the purchase volume would go up as consumers look to see which other monsters they could reveal...

The campaign started last year and I can't see (via googling) how it has gone but everyone is a sucker for cartoon monsters (just me then?) and it would be interesting to see what impact this has had on brand metrics, sales and of course recycling / retention of crisp (chips) packets!

I tried to interact with the site, but Brazillian defeated me:

The Doritos Brazil site didnt have an English option , as you can tell!