I’m doing this twice a day currently. (Sorry, physical therapist I met on Monday.)
Clamshells
30 reps on each side.
Reverse Clamshells
20 reps on each side.

Source: Runner’s World
Similar to clamshells, except you hinge at the knee instead of the ankle to work different muscles in the hip area. I like this awkward-looking drawing because I feel awkward when I do them.
Sidelying Leg Lifts
25 reps on each side.
I have to make sure my hips are rolled forward a bit in order to feel this where you’re supposed to feel it. But once you are in the proper position, it burns!
Bridge
Hold for one minute.
Marching Bridge
10 sets of marches.

Source: Women’s Health
From bridge position, lift one leg as if marching without moving the hips. Lower and repeat with the other leg. That is one set.
Single-Leg Bridge
10 reps on each side.

Source: SoccerAthletics.com
Cross one leg over the knee and raise up to bridge position. Hold for a beat, then lower back down.
My glutes/thighs are usually on fire by the time I get to the single-leg bridges, and I typically don’t make it through all ten on each side. Wednesday’s physical therapist (who sent me three of these exercises) said it is better to not do an exercise than to do one with bad form. So if you feel your form disappearing on any of these exercises, stop the workout. Focus on quality versus quantity.