Register your American Express Card via this link to get 5 downloads of any MP3 single from iTunes for free. That's the best such deal we've seen from American Express. You must use the registered card to purchase the five songs from iTunes. A credit equal to the five songs plus tax will be applied to your statement typically within five business days; however, the credit may take up to two billing periods to apply to your account. Corporate cards and gift cards are not eligible for this offer. Deal ends March 15.