The Plateau Effect - Legs

I've been working out consistently since the end of February. It took a little time but I finally found a workout routine that works for me. I started out concentrating on cardio only and slowly but surely I've successfully added strength training to the mix. I work my upper body twice a week. I exercise my biceps, triceps, back and chest. I also do several abdominal exercises. I've been varying my routine to get the maximum effect and so I won't get bored. Sometimes I use the weight machines and other times I use free weights. For abs, sometimes I do crunches on the exercise ball, hanging knee raises or crunches with a medicine ball on an incline bench and planks. Additionally, I do cardio five times a week. The results have been pretty good.

One thing I noticed, however, is that I don't vary my leg exercies as much and I don't see any significant difference in my legs from when I started working out. I work my lower body twice a week and I generally do the leg press, leg extensions and leg curls. What else is there?

Well, I've done some research and apparently there are a ton of other things I could be doing to tone and strengthen my legs and tighten my butt. I've decided to add squats:

lunges:

and calf raises to the repetoire:

When I first started working out I had a trainer for a week. He had me doing calf raises on a machine and I literally, could not walk for a week! I've shied away from that machine ever since. I think I should be pretty safe with these though.

The goal is great legs by the end of the summer.