Squats, front squats, and deadlifts (both regular, with the knees bent as well as straight leg style). Make sure your form is right- keep your back flat or arched, and make sure your hips go back when you squat down (rather than going down towards your ankles). I tell people think of how you squat over a dirty toilet, not how you would go in the woods (mental image that most people can relate to!) Also, don't listen to the people who tell you not to squat low- deep squats (top of thigh parallel to ground or lower) are the best way to get to your glutes.
Start with sets of 8-10 while you're working on your form then start working your way up in weight & down in reps.
Jump squats are fun, too. If you want to try them, use about 30% of what you normally put on the bar for regular squats.