The forces and torques among macroscopic objects caused by fluctuating quantum fields are known as Casimir effects after the Dutch theoretician who discovered them in the late 1940's.  Recent high precision experiments and emerging micro-electromechanical applications have generated great interest in the nature, properties, and manipulation of Casimir effects.  I will discuss the origins, interpretation, and computation of Casimir effects.  In particular I will outline the development of a powerful method to compute Casimir forces and torques based on classical scattering theory.  I will survey some of the results obtained with these methods.