I like this interactive library bulletin board idea: quotes or clues about books laminated on squares with the answer (book cover) stapled underneath. Lift the flap to check your answer. Could be a theme bulletin board, too.
A fabulous display from Yulia celebrating all things nautical. A quiz was included in this display - hidden pirate scrolls could be unfurled to reveal questions and at the end of the summer the children were awarded small prizes for their answers.