UPDATE: This offer is expired. You can find the best current offers here.
Through December 19, 2011, American Express is offering a 45,000 mile sign-up bonus after spending $3,000 on the Gold Delta SkyMiles credit card within three months. This offer applies to both their personal and business credit cards.
This is much better than the standard sign-up bonus of 30,000 miles, though it only requires $500 worth of spend in the first three months.
If you haven’t signed up for a SkyMiles credit card yet, this is about as good as the sign-up bonuses get…