As Captain G mentioned in his earlier post Starwood currently has a stay 2 stays get 1 weekend night promotion. There are more reasons to take advantage of this promotion as Starwood is also offering 1000 Delta miles or 1000 Northwest miles with each stay. The only catch here is that not all Starwood properties are participating in the 1000 Delta/Northwest miles promotion. Here is a list of the participating Starwood properties.
Also, regarding the Priority Club free weekend nights promotion that I touched upon in my previous post, I recently read the fine print and realized the free weekend nights are in lieu of Priority Club points. This essentially means you will not be receiving Priority Club points during this promotion period. More reasons to stay at Starwood instead.