This is one bad-a** exercise to do if you want to increase the difficulty of your glute workout. Not only does it add weight to your movements, but it takes a tough bodyweight workout and focuses it mostly on the glutes.
While it's not ONLY going to work out your glutes (it hits your hips, thighs, and lower back as well), it's one of the best exercises to add mass to your ass!
Lie on your back on a Yoga mat. Place a barbell across your lap, setting it so that the bar runs across your hips. Once the bar is situated, bend your knees and place your feet flat on the floor.
Push your feet into the floor and thrust your hips toward the ceiling. You may need to hold the weight on your laps with your hands, but make sure to focus on using your hips and glutes to thrust forward.
Talk about a tough workout targeting your glutes!