Positrons (the antiparticles of electrons) and positronium (the bound state of an electron and a positron) are currently employed in the exploration of fundamental effects ranging from condensed matter physics to astrophysics as well as in the diagnostics of living biological systems and of the electronic and structural properties of industrially important materials. Our main research interests are in atomic physics problems where beams of positrons and positronium with speeds comparable to those of atomic electrons are contributing to the unravelling of general collision phenomena as well as illuminating specific interactions and processes such as exchange and annihilation.