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.

Nana’s Paradox covers Source games and runs articles and news about maps and mods.

Netday is dedicated to custom maps of high quality only. Maps are added regularly (at least one per week). It also covers mods like Dystopia, Portal Prelude and JailBreak. The map reviews are both in English and in French. It is advert free and features direct download to all files.

Pájaros de Barro is a Spanish Gaming Community which offers public servers and support (tutorials, videos, forums, articles…) for Team Fortress 2 and Left 4 Dead as well as updated and fully spanish translated news and interviews related to Steam and Source Engine based games.

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

Planet Half-Life is the daddy of them all. It’s been online longer than most and is generally updated daily.

PlanetPhillip.com contains the most comprehensive database of single player maps and mods for the Half-Life series of game on the Internet.

SLUM is Czech Steam community and fan portal about Steam and Valve games.

Steam Friends covers all the news related to Steam and Valve.

Stu-Pidaso is a website aimed at Half-Life and everything related to it.

The Survivors Diary Podcast is a weekly podcast about Left 4 Dead where we explore certain features of left 4 dead, as well as talk about community stuff that has been released. They also now cover maps that people have made as well as discuss tactics, suggestions and even glitches for the game. THey hope [...]

Team Fortress HQ provides the latest news, articles, skins, maps, sprites, and everything else Team Fortress you can imagine.