It's not a foldable, but I really like this interactive notebook page idea. I (secretly) look for excuses to get out markers. This page has colors that actually have function. I've posted before about using color with a purpose, which basically means having students color-code their notes. One nice thing about this page is that you can change the example problems based on the class period. I always seem to have class periods that struggle and class periods that fly through things. You could use different examples throughout the day, depending on the class.