A great leg movement that requires very little equipment, just a barbell and a three-foot chuck of 2x6", is the Hack squat. I'm referring to the upright sissy squat hybrid, not the reverse deadlift type that's popular in odd lift contests these days. Those do little for development.
A single set of Hacks after your last set of heavy flat-footed barbell or trap-bar lifts will set your quads on fire. As depicted below, the Hack squat should be performed with an upright position, and the bar should be planted firmly behind your butt with an underhand scoop grip. Squat down to just below parallel, pause, and rise.
You don't need much weight, perhaps 125 or 135 pounds for a guy who does his last set of squats with 350 to 400 pounds. A routine would like like this:
- Full Squat: 3 x 6-8 reps (increase weight 25% on each set)
- Hack Squat: 1 x 12-15 reps with 50% of your first set of full squats.
After working the Hack squat for a few weeks, you'll find a pleasant increase in muscular endurance, jumping ability, and quad shape. You'll also see benefit to your heavy squatting.