This review volume is intended to survey the field of quantum fluctuational phenomena induced by material bodies, which is commonly encompassed under the name of Casimir physics. H B G Casimir first discovered that zero-point fluctuations in the electromagnetic field caused an attractive force between closely separated metallic plates. Now - 75 years later - the field is burgeoning, with numerous experimental verifications and applications to practical devices starting to emerge. In this book, new ideas about Casimir physics are brought to bear on such diverse subjects as cosmology, where the Casimir energy may explain the dark energy that causes the cosmic repulsion, and nonstatic regimes, such as Casimir or quantum friction. Unsolved problems, including divergences in Casimir self-energies, the meaning of local energy densities in inhomogeneous backgrounds, and discrepancies between theory and experiment, are treated in some detail. It is hoped that this collection of papers will serve as an introduction to the field for newcomers to the subject, and that it will inspire a new burst of research into the nature of the quantum vacuum.