I'm already discovering new resources, even as I pull them for the open house. We have a bunch of lateral thinking puzzle books, including a few that focus just on math! We moved those out of the 700s to be with the other math books in the 510s. There are still puzzle books if teachers need some extension ideas.
The challenge will definitely be how to keep track of all our great resources. Keep checking back here for more pages. I will active them as I finish.