I was watching some TV show the other day and it showed a guy performing squats in a way that I've never seen before. Instead of the traditional way with the barbell across his back, he had the barbell infront of him, resting across his collar bone with his arms crossed infront of him. What does this do different the having the barbell across your back?

It's called a front squat and it works primarily the front of your thighs, the quadriceps. The other squat (back squat) works the butt as well as the entire leg.

Front squats are a big part of Olympic Weightlifting training re the Clean & Jerk. However, they are not done using the crossed arm method, but rather with a pronated (palms away) just wider than shoulder width grip and elbows way up high so the weight is resting on the clavical (Collar Bone) instead of on the arms. Takes a bit of getting used to due to the flexibility required in the wrists, but it's really the only way to do this exercise effectively when using heavy weight. Usually one can't do the same anoumt of weight as with the traditional back squat. I've found if my back is bothering me to the point where I can't do back squats, I can still do an effective front squat because your back is far more Vertical position wise and that takes some strain off the lower back area. Try them!