It's well known among the miles and points community that Intercontinental Hotels Group (IHG, nee Priority Club) offers some really generous promotion codes that can be used periodically. These codes are usually 4 digits and you can easily register for them prior to an upcoming IHG stay. Other bloggers have covered this at length, so I'll just point you to a good link at "Head for Points" where the process of registering is covered.
I'd also like to share my personal results from a recent stay:
Unfortunately, this kind of result isn't endlessly repeatable, because many of the most lucrative bonuses (such as the "Elite Member Next Stay Bonus") are "one time use" codes. Still, you can usually get this kind of result at least once a year and the bonuses will usually be triggered by any IHG stay, whether it's a $79 Holiday Inn Express stay, or $400 at an Intercontinental.