A couple of years ago I spent a weekend making this: http://imgur.com/a/Kp35g

I don't claim to be brilliant with carpentry so it was a mixed success, but you can adjust between a sit down and stand up desk, it cost about £50 all in. I'm not sure it would work on a larger scale, I had a very small room and just needed something to put my laptop on.

Apologies for the photo quality, first generation iPhone.