About.com : http://www.macmerc.com/news/archives/1270. Pepsi is doing a big giveaway where if you find the right bottle top, you can get a free iTunes song.
Here’s a good post in about.com that explains how to tell if the bottle is the right one:
# You find a bottle that has a yellow top. Diet Pepsi, Pepsi and Sierra Mist all have them.
# Tilt the bottle 25 degrees and look through the bottle till you can see underneath.
# If the letters say AGAIN, then pick something else. If there are series of random letters, you have a winner.
# Buy the bottle. Drink. Get new song P-)