[UPDATE: Although the mailer I received contained no promo code, some readers are reporting that when they call Chase they are told the rep knows nothing about this promotion. The mailer did not say I needed to register, suggesting that if I met the spend minimums the bonus would be applied. YMMV.)
Continental (er...United) is offering cardholders of its now-defunct Presidential Plus card (that's the one that gives you lounge access) double miles on all purchases through April 30th.
This is a great deal, except for the following 2 caveats:
1) The double miles don't kick in until after your first $2,000;
2) You can only earn 50,000 miles during March and April.
The second one isn't a big deal for most people, but that $2,000 hurdle is a big one for most people. However, if you're not working on hitting a spend minimum on another card (many of us are working on that Amex PRG Business card from a couple of weeks ago), and you spend more than $4k/month, it'd be worth moving your spend over to this card (assuming you have it) for 2 months and maximizing those United miles.
Find out when and how you can get the most from a Continental Airlines credit card at Creditcardsguidance.com.