Bridges are an awesome way to target your glutes, and this version kicks the burn up a notch.
To do it: Lie on your back with both knees bent, feet flat on the floor, and arms extended by your sides, palms facing down.
Press your left heel into the floor (lifting your toes off the floor) and bend your right knee in towards your chest, flexing your foot.
Press your hips up off the floor as you extend your right leg out beside your left knee, pressing out through your heel.
Lower your hips and bend your right knee back in, only tapping the floor with your tailbone (don't lower all the way back down). That's one rep. Repeat up to 20 times and then switch sides
Options: If the kick is too complicated, just work on a single-leg bridge and keep your right knee bent into your chest as you lift and lower.