I haven't seen this posted anywhere, but if you sign up for marriot rewards (free) and stay two nights in marriot brand hotel in 120 days, you can get up to two free nights. I used points to buy marriot certificates so I'm not even spending the money on the hotel stays.
There’s plenty to love about Marriott Rewards, from exclusive benefits to 250+ rewarding opportunities. Now, with MegaBonus, there’s even more.
To earn up to two free nights:
Register by March 31, 2014
Stay between February 1 and April 30, 2014
Earn a free night at a category 1-4 hotel after the second paid stay External Window, up to two free nights
With 3,700+ hotels across 14 distinctive brands, Marriott Rewards is spreading the love.
For more information, contact Marriott Rewards Customer Support at 888-MARRIOTT (627-7468)
Marriott Rewards Customer Support
https://www.marriott.com/rewards/promotion.mi?promotion=MS14&aff=MARUS&affname=6149885&co=US&nt=CJ