BALROG - Genealogy & Chronology of Roguelike games
Home of the Underdogs - Great listing of older roguelikes
Roguelike Restoration Project - The Roguelike Restoration Project's goal is to find old roguelike games (eg., Rogue, XRogue, UltraRogue) and fix them up so that they can run on current Unix and DOS/Windows platforms.
Roguelike Graveyard - This is the place for all dead roguelike games.
roguelikedevelopment.org - Extensive collection of articles on roguelike game development