While they could use a little help in the aesthetic and presentation departments, I'm impressed with Hong-Kong-based Oasis Concepts' folding furniture line-up. What they've done is worked out some simple mechanics with basic hinges to fold a table flat, then applied that system to multiple pieces: Kitchen chopping tables, kitchen islands, dining & buffet tables, side tables for entertaining and even desks.
Here's how it folds:
Simple, no? Here's a vid of it being both folded and unfolded:
And of course, a key benefit of designing this type of product is that you can ship it flat, and yet it still arrives fully assembled. Oasis, if you're reading this: Since you're saving a couple bucks on not having to print up assembly instructions, throw that cash into some better videos!