One of my friends did a scrappy that I'm contemplating for myself. She worked with foundation such as a dryer sheet, put an odd shaped piece in the middle and then worked her way out with various shapes. No plan, just sew. Once the sheet was full, square it up and there's one block. Repeat.
I have done a rail fence with black and white but that takes more fabric and not really one to use up a variety of leftovers.