Lunges are great for toning your thighs, and this sliding version works nearly every muscle in your lower body.
Begin in a runner's lunge with your right leg forward, hands on either side of your right foot, and left leg straight (the paper plate should be under your left foot). Bend your left knee and slide your leg into your chest, squeezing your knees together. Quickly extend your left leg back out to your full lunge. That's one rep. Do 15 reps on the right leg, 15 on the left.
Tip: Pull your belly button into your spine as you slide your knee in to really engage your abs.