Review article by Sean Carroll (Caltech) on one of the most important open cosmological questions: the physics behind the acceleration of cosmic expansion. Requires undergraduate physics knowledge. Published in the electronic review journal, Living Reviews in Relativity

Brief overview of the role of the cosmological constant in modern cosmology, using mathematics at an undergraduate level (and, rarely, beyond). Includes a list of technical articles and links. By Eli Michael (University of Colorado at Boulder).

Homepage of a research project based at Lawrence Berkeley National Laboratory, dedicated to using observations of supernova explosions to measure the distance of far-away galaxies; this, in turn allows one to map the properties of cosmic expansion.

A review of the basic idea of the cosmological constant, and of proposals to replace it by a time-varying field. By Michael Doran and Christof Wetterich.

Project aiming to understand why the universe is accelerating and not being slowed by the mass it contains.