Half-Life 2

Bad At Games
Cheat codes and hints.
http://www.badatgames.com/cheats_119887_pc_halflife_2.html

Counter-Strike Game Zone
Forums for game and technical discussions.
http://www.csgamezone.com/

Dedicated Server Console Commands
A list of console commands for Half-Life 2 Dedicated Server.
http://www.xdude.com/hl2dedicatedserverconsolecommands.htm

Filefront
Offers downloads and news of modifications, maps and patches.
http://halflife2.filefront.com/

FilePlanet
Demos, wallpapers, movies, trailers, maps, and modifications.
http://www.fileplanet.com/93939/0/section/Half-Life-2

GameFAQs
FAQs, cheats, reviews, and a message board.
http://www.gamefaqs.com/computer/doswin/data/914642.html

GameSpy
Includes cheats, interviews, videos and articles.
http://pc.gamespy.com/pc/half-life-2/

Half Life 2 Files
Character information, screenshots, news, weapons, story line, game FAQ, cheats, skins, mods, models, maps and game utilities.
http://www.halflife2files.com/

Half-Life 2
Official site. Includes screenshots, trailers, and a game overview.
http://www.half-life2.com/

HL2C
Game information, weapons information, character information, FAQ, forum, chat room, polls, interviews and game reviews.
http://www.hl2central.net/

IGN
News, press releases, previews, reviews, cheats, FAQs, screenshots, and videos.
http://pc.ign.com/objects/492/492830.html

Laggfree
Includes guides, forums, and downloads to help reduce lag on servers.
http://cpnclan.home.comcast.net/

Play.tm
Gives news, images, video and downloads.
http://play.tm/indepth/half-life_2

Punk Ass Fraggers
Offers forums, news and system tweaking guide. Includes downloads area with maps and modifications.
http://www.punkassfraggers.com/

Source Dedicated Server
Server resource for HL2-based games. Includes a discussion forum and knowledge base.
http://www.srcds.com/

Team Xbox
Information, screenshots, and a preview.
http://games.teamxbox.com/xbox/1200/HalfLife-2/

Wikipedia: Half-Life 2
Encyclopedia article on the game covers backstory, plot summary, gameplay, awards, add-ons, derivative works, technical specifications, and soundtrack.
http://en.wikipedia.org/wiki/Half-Life_2