A personal trainer once told me that you can't lose fat off a certain part of the body ... weight loss/gain is genetic and your body will take it from where it's programmed to.
That said, good toning exercises for the legs (you may see a difference in muscle tone, which will help the legs' general shape) are squats, running, leg lifts (done properly these also work your core and side muscles), calf raises and the reverse kick (go on the floor on all fours, knees spread shoulder width apart. Slowly and controllingly lift one leg so it is completely extended in the air behind you. Hold for five seconds and slowly bring it back down. KILLS the ass muscles!)