Spotted this in the Worthing branch of Sainsbury's, but it appears to be nationwide.
Get a free £15.00 voucher for music downloads from iTunes when you buy any two from a selected list of chart CDs priced at £9.97 each.
The list was a bit limted, about 20 different CDs to chose from, but they did have the new albums by Snow Patrol, Kaiser Chiefs and Anastasia to name a few.
I was going to give the CDs as Xmas pressies anyway, so I've got myself £15.00 of downloads for free! Nice!