Popcorn Maths - solving random math problems I will obviously have to make it appropriate for 8th grade, but I foresee using this for SLOPE. Maybe in enrichment class.

Laminate a number ladder, cut small slits in top & bottom & add a pipe-cleaner with a small bead. Use the bead to slide up & down as you complete addition & subtraction problems (",)

Check out this highly rated math manipulative that students LOVE! These addition and subtraction sliders are a great way for students to practice their skills.