I believe I have the solution for riddle number two; the front guy's hat is black. The logical process is as follows:

Of necessity, at least one person has to be wearing a black hat. If the two guys in front were wearing white hats, the person in the back would know that his hat was black, meaning that the front two hats are either white/black or black/black. The guy in the middle realizes that the guy in the back knows this; if the front guy's hat was white, he would know that his hat was black. As the middle guy does not know the color of his own hat, it stands to reason that the first guy's hat is black.