Back Squats-

Front Squats-

Power Squats-

Box Squats-

Barbell Lunges-

Quads- Stretches

Static Quad and Hip Flexor Stretch-

Lunge Stretch-

Standing Quad Stretch-

Quadriceps

Hence its name, the quadriceps are composed of four different parts.  The Rectus Femoris is the biggest section located in the middle of the front of the thigh.  THe Vastus Medialis and Vastus Lateralis lay to the left and right of it.  Below the Vastus Lateralis is the Vastus Intermedius just above the inside portion of the knee.  Together they all work to extend the knee straight at the knee joint much like the triceps do at the elbow.