In celebration of the iTunes Music Store reaching half a billion songs sold, Apple is giving away to the 500 millionth buyer: 10 iPods of their choice (any model), a 10,000 song card for the iTMS, 10 gift cards carrying a 50 song weight, and a trip for four to a Coldplay concert.
Apple is giving away an iPod Mini and a 50 song gift card to the purchaser of every 100,000th song sold until they reach half a billion. This promotion starts at the 480,100,000th download and runs until the 500,000,000th song is sold.
[Update:] The 500 millionth tune was sold between 21:00 and 22:00 UTC on July 17, 2005 (between 5pm and 6pm U.S. Eastern Daylight time).