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.