Here some more you can do.
Front Squats for the quads. Same as regular squats except that you hold the bar in front of you. Just have the bar on your front delts with your arms folded under it to hold. Try placing a towel or some between your arms and the bar to provide some coshion. Its a little akward at first but its a really good excercise for the front quads. Remember to keep your back straight.
Another one you can do is Stiff leg deadlifts for the hamstrings. Remember to keep your back straight and your knees slightly bent. Use an alternate grip (one palm faacing in and the other facing out). Don't lower the bar to the floor but just slightly below the knees to your shins. It really works your hamstring really well.