Ever heard of the Cossack Squat?
It is "a lateral squat movement that develops dynamic flexibility in the hips, groin and hamstrings, as well as ankle mobility. It also develops specific strength in the quads, glutes and hamstrings, as well as core strength and stability." (from www.defrancostraining.com)
They are relatively easy to execute, yet challenging enough to give you a good burn. You can do them anywhere, any time, with or without any equipment. Try it today!