We have $15,866,535 million in bonuses to Brown, Chambers, McMichael, Carter, & Taylor that can be restructured and prorated over their current 4 year contracts. Not likely, but if all were done would save $11,899,901.
Also, we have $19,800,000 in salaries to Thomas, Taylor, Frerotte (if not cut), Booker & James could also be restructured if needed.
Washington & Broncos makes cap room by converting salaries to prorated bonuses on a yearly basis. Helps cap in short term, but puts more and more money on future salary caps. All teams do it to some degree. But not as much as the others because either they don't want to pay that much up front bonus money and/or are trying to manage the cap long-term.
Check out Finheaven's Salary Cap page. Provides a lot of info. And thank Clumpy if you get a chance who puts it all together.