I think an article on splines (Catmull-Rom..., natural cubic splines...) would fit very nicely with the rest of the material, perhaps right after polynomial approximations.
Another question that pops up a lot is target leading, which in the usual case of constant velocities can be reduced to a quadratic equation by using the properties of the dot product. So perhaps a lesson on the dot product and its applications would be in order. Other applications could be things like ray-sphere intersection, orthogonal projection...
Just some ideas. I'll post back if I can think of any others.
