Valve Community

HL2World.com is a news and forum based site that has been around for a long time. The forum is particularly active.

3D Buzz is a company dedicated to providing the world with quality technical education over 3D animation, programming, game design, and much more. They have been producing training videos since 2001, always pushing the envelope in the development of informative lessons with an engaging and personable format. They try to make the viewer feel more like they’re involved in a classroom discussion with an energetic teacher as opposed to being stuck in a dry, uninspired, run-of-the-mill training video.

PCosmos is a great list of Half-Life maps and mods. It is also available in French.

Modifikace is a Czech news and review site for single player Half-Life 1.

Can You Run It? provides a one-click solution that looks at your computer’s hardware and system software to determine whether or not your current system can run a product.

Map-Factory is a database hosting custom maps for any FPS. If you’ve make a map or simply came across a good map, feel free to submit it! If not, then just navigate through the site and you’ll find a lot of good maps!

L4D.es is a website and Spanish Community dedicated to Left 4 Dead. Pagina web de Left 4 Dead en Español.

City 17 is a Russian review site for single player maps and mods.

My Aperture Labs: Welcome to the Aperture Science Enrichment Center’s Online Community Networking Web Service (or ASECOCNWS for short). Here at the ASECOCNWS, test subjects may attempt to solve Portal puzzles, build their own Portal puzzle environments, or simply talk about cake.

Ten Four is a well known single player review site that covers a few different games. They present 3 levels of awards for the better releases and the forum, whilst not as busy as they used to be, is still a place to find the latest releases.

Black Mesa is a third-party total conversion modification for Half-Life 2 and a remake from the 1998 video game Half-Life. The ultimate goal of the mod is to recreate the original Half-Life from the ground up, using the advanced capabilities of the Source engine to create a new and more engrossing in-game world.

TF2Portal.es is a spanish website focused on Team Fortress 2. Some of the contents are: news, downloads, tutorials, forums and a public server.
TF2Portal.es es una web en español dedicada por completo a Team Fortress 2. Algunos de sus contenidos son: noticias, descargas, tutoriales, foros, y un servidor público.