Colossal Cave Adventure (aka Adventure): Rogue's progenitor 
Rogue: The original Roguelike
Moria: A Middle Earth/Tolkien inspired Roguelike
Omega: A Roguelike known for breaking out of the dungeon
Larn: A Roguelike featuring towns and an overworld
Hack: An early Rogue clone
ADOM: A Roguelike released in 1994 with a detailed storyline
Angband: A Roguelike inspired by Moria, also following Tolkien mythology
Nethack: A Roguelike based on the original Hack
Linley's Dungeon Crawl: A Roguelike that inspired Dungeon Crawl Stone Soup
Tales of Maj'Eyal:  A Roguelike previously inspired by Moria/Angband that branched off and developed it's own story, powered by T-Engine4 an open source Roguelike engine.
Dwarf Fortress: A massively popular Roguelike with world-building elements

OpenRXL: Roguelikes based on classic NES games
SpelunkyWorld: Official website of the Roguelike Platformer game
Vulture: A graphical UI for Nethack, Slash'em & UnNethack with more variants being developed
Dungeon Crawl Stone Soup: A Roguelike inspired by Linley's Dungeon Crawl
Cardinal Quest: A commercial arcade style dungeon crawler, inspired by Gauntlet and other games
Powder: A cross-platform Roguelike, also available for owners of homebrew GBA and NDS carts!
DoomRL: A Roguelike based on Doom and bathed in blood, now with graphic tiles!

A brief History of Rogue: The story behind the game by Glenn R. Wichman
Actively Developing Roguelikes: List of new, current & actively developed Roguelikes
International Roguelike Database: Roguelike database provided by Temple of the Roguelike
Diggr: A fresh, new outlook on the Roguelike genre
Bay12Games: Home of Dwarf Fortress, forums and more
Do you want your Roguelikes identified?: Active Roguelike discussion thread at SomethingAwful
The Roguelike Thread: FacePunch's mega discussion thread on Roguelikes
Roguelike Archive: List/Archive of old Roguelikes
Grand Rogue Auto: A Grand Theft Auto Roguelike
Dinofarm Games: Home of 100 Rogues, a zany IOS Roguelike

Roguelike Radio: A podcast about Roguelikes
Temple of the Roguelike Channel: Official TotR Youtube channel 
The UberHunter's Roguelike Channel: Youtube channel with RL gameplay videos
Britzl's Roguelike Game Feed: RSS Feed for Roguelike Games
Planet Roguelike News Feed: RSS Feed for Roguelike News & Development (not original Elderlore)
Temple of the Roguelike: Roguelike News/Forums
Roguelike: Steam Community
TIGForums: Indie gaming forums 
Angband.oook.cz: Angband News, Comics, Forums & More
Rogue Life: Roguelike news and game portal

RogueBasin: Roguelike Information Resource & Wiki
Roguebasin Articles: Series of articles on programming Roguelikes
Rec.Games.Roguelike.Development: Roguelike Discussion Group
The Chronicles of Doryen: The home of Libtcod, a Java library for Roguelikes
FPC Valkyrie: A FreePascal RL Development Library by the award winning maker of DoomRL
Rogue Bard: Free music for free games
Dijkstra Maps: A method of generating maps in Roguelike games
Trystan's Roguelike Tutorial: Complete Roguelike Tutorial for Java+Eclipse
Trystan's Nameless Roguelike: Completed example for his Tutorial
Jotaf's Complete Python+Libtcod Roguelike Tutorial: Complete Roguelike Tutorial
Rick Clark's Complete Freebasic Roguelike Tutorial: Complete Roguelike Tutorial
RogueClone IV: A complete, open source clone or the original Rogue in C
Roguelikedev on Reddit: Reddit's Roguelikedev feed
How to write a Roguelike in 15 steps: A tutorial on Roguelike Structure (no code)
NV Java Roguelike Engine: A Roguelike engine for Java
Yarn: Yet Another Roguelike eNgine for Java
Roguelike Development Megathread: Discussion on Roguelike Dev (Bay12Games Forums)
Roguelike Library for Java: Roguelike library for Java
Jade Rogue: Roguelike library for Java
PSC's Roguelike Project Page: Standard Design Doc & Breakdown for a Roguelike
Roguelike Game Maker: A RL engine being actively developed
Tyrant: Open Source Java Roguelike/Engine
Angular-Angel's Roguelike Engine: A promising RL Engine written in C++ being actively developed
PYendor: An open source Python+Libtcod RL Engine being actively developed
Neon: A Java based RL Engine being actively developed (Alpha)
The Roguelike Restoration Project: A project to further develop old RL games, hosted on SourceForge
BeCoding's Open Source RL List: A list of open source Roguelikes
OSTATIC Open Source RL List: Yet another list of open source Roguelikes
QHack: Guide/Tutorial with source code for Roguelike Programming in C

The Interactive Fiction Archive: The #1 archive of all things IF
Rec.Games.Int-Fiction: Interactive Fiction Discussion Group
Creating a Text Adventure in Java: Complete Text Adventure Tutorial for Java
Terry Cavanagh's Text Adventure Tutorial: Basic Structure & Code for Basic/Freebasic

TIGSource:  Popular indie game news & development site
DIYGamer: Indie news, reviews & development
The Game Creators Forums: Dev forums for DarkBasic & TGC Developers
CodeBlocks: Home of the popular Cross-Platform IDE
FreeBasic.net: The official home of FreeBasic
FreePascal.org: The official home of FreePascal
Python.org: The official home of Python
PyGame: The popular Python game development library
DiveIntoPython: A great tutorial series for learning Python
SoundJax: Sound Search Engine