"The Theory of the Universal Wavefunction", Hugh Everett III, in The Many-Worlds Interpretation of Quantum Mechanics, eds. DeWitt, B. & Graham, R.N., Princeton: Princeton University Press, 1973.
Hugh Everett III's 1955 Phd dissertation, presenting the original 'no-collapse' interpretation of quantum mechanics.
"Mindless Sensationalism: A Quantum Framework for Consciousness", Don N. Page, Consciousness: New Philosophical Essays, 2002.
Presents an Everett-style interpretation of quantum mechanics and discusses its relation to a consciousness in the framework of observation selection effects.
"The Mathematical Universe", Max Tegmark, Foundations of Physics 38(2):101-150, 2008,
This is the "full-strength version" of Tegmark's 'Theory of Everything', which develops the idea that all mathematically self-consistent structures are physically real (a form of all-possible-worlds-actually-exist theory). Tegmark conjectures that all and only computable and decidable (in Gdel's sense) structures exist, which alleviates the cosmological measure problem and helps explain why our physical laws appear so simple. What makes Tegmark's approach highly interesting is that he takes the first steps towards making such a theory quantitative and capable of generating empirically testable predictions.
"Decoherence and Ontology (or: How I learned to stop worrying and love FAPP)", David Wallace, in Many Worlds? Everett, Quantum Theory and Reality Wallace, eds. Saunders, S; Barrett, J; Kent, A; Wallace, D, 2010, Oxford: Oxford University Press.
Argues that decoherence solves the 'preferred basis problem' with many-worlds quantum mechanics, in the context of an emergent picture of high-level ontology, and that the question 'how many worlds' is a pseudo-question.
"What is Probability?", Simon, Saunders, in Quo Vadis Quantum Mechanics, eds. Elitzur, A; Dolev, S; Kolenda, N., 2005, Springer.
Argues that the 'probability problem' in Everettian QM can be solved, and that probability actually fits more naturally into EQM than into a one-world view.
Saunders, Simon & Wallace, David, "Branching and uncertainty", British Journal for the Philosophy of Science 59(3): 293-305, 2008.
Proposes a way of making sense of self-locating uncertainty in Everettian QM.
"The Many-Worlds FAQ", Mike Price, 1995.
Frequently asked questions about the many-worlds interpretation of quantum mechanics. A classic usenet document. One frequently asked question it omits is: "What has Mike been doing after he wrote this document (his previous active Internet presence having ended abruptly)?" Answer: Playing chess.