Meg, do unilateral leg presses with your feet (foot) high on the platform. Go as deep as you can on it.

You can also do partial deadlifts from a power rack. Set the pegs at just below knee height. Bend down (keep back straight) and pick up the bar with both hands. Stand straight up. Do 3 sets of these. 8 reps, 6 reps, 4 reps. Increase the weight on each set. Make sure you are sticking your but out a little when you do them, but still maintain a flat back (kinda like you are squatting ... or about to sit in a chair)

Are you doing step-ups? They are a good fanny buster.

Also, try supersettting lunges with back extensions. When you do the back extensions, only go down about half the way, then back up and REALLY sueeze your glutes at the top. If you don't feel it, hold a weight plate across your chest.