This might be the best "before and after"/upcycle/DIY furniture/make-the-best-with-what-you've-got project ever.
Say you have an old mattress and box springs set, but your tastes lean a bit modern/minimal and you have your heart set on a low, platform-style bed. Sure, you could go buy brand new everything -- OR -- you could do what Katy at The Clever Bunny did and turn your box springs into a platform bed for cheap!
This project is really quite brilliant, don't you think? Check out how it's done right here.