Planet Half-Life:Resource includes files, forums, modifications, articles, and daily news.
CICS: Forums for each game, as well as technical support and off-topic chat.
Half Life Source: Offers news, guides, screenshots and a forum.
Half-Life Portal: Includes guides, walkthroughs, reviews, and a forum. Also offers a media area with videos and screenshots.
Half-Life Prototype Developers: User submitted articles on the Half Life series. Includes tutorials on server administration and mod development, and technical articles on the game engine.