I'm vegetarian, and my main sources of relatively low carb-to-protein are:
Fage 0% FF yogurt
Friendship 1% cottage cheese
Cabot 75% FF cheese (TONS of protein!)
Frigo LF mozzarella cheese sticks
Egg whites (scrambled and hard boiled)
On a weekday I am able to get around 40% protein / 150 grams. I'm bad on the weekends though
and only get around 20% but I figure if I can stay under calories, it's a tradeoff.
There's also fat free feta, but I think it tastes vile.