Aviezri Fraenkel: A comprehensive bibliography on combinatorial games; several papers about combinatorial games; and information about where to publish such results.
David Eppstein - Combinatorial Game Theory: Many up-to-date links, and a short introduction.
Dice Theorem: How many ways are there of throwing n indistinguishable dice each with m faces?
Elwyn Berlekamp - Combinatorial Game Theory: Elwyn's research in the field, including several papers.
Erik Demaine's Combinatorial Games: Research on pushing blocks, Clickomania, Phutball, and sliding coins. Survey paper on algorithmic combinatorial game theory.
Games that interest John Conway: Clever Games for Clever People, from the book On Numbers and Games.
Jeff Erickson - Mathematical Games, Toys, and Puzzles: Links to several game theorists and actual games, plus a brief introduction. Also a couple of papers on game theory, about Toads and Frogs and Sowing Games.