American Express is offering their Business Platinum card free the first year. Make sure to print the terms and conditions of the offer which put the fee waiver in writing. The usual annual fee is $300.
The key benefit is lounge access with Delta, Northwest, and Continental (you must be flying the carrier on the day of travel and can only use the lounge of the carrier you’re flying). Ancillary benefits include Gold status with Starwood and Preferred Select status with Avis.
I don’t usually recommend this card (though I have one myself). With a free the first year offer, however, it is a way to get lounge access for a year…
UPDATE November 16: Amex has pulled the no fee component of the offer already.