On Hotels.com, book a hotel room at select properties from 11/29/13 to 12/2/13 and travel by 12/15/13 to get your second night for $1!
There’s a limit of one $1 room per booking and you may be required to pay taxes and fees on the second night.
In addition to this promotion, if you use your mobile device to book only on 11/30/13, you can save $20 on a booking of $200 by using the code MOB25THANXUS. This promotion is for US customers only.
Hotels.com also has a rewards programs called Welcome Rewards where for every 10th night booked, you get one free. The free night has no blackout restrictions and can be used for any hotel that has room availability on their website.