Interlopers has been online since 2004. It posts selected Steam game news but its focus is on content creation.

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

L4D Inside is a Russian L4D portal.

The L4D Map Database is a library of all Left 4 Dead maps (official and custom) in the form of a wiki that anyone can contribute to. Includes downloads, screenshots, videos, information, and more for each map.

L4D Maps is a website completely dedicated to Left 4 Dead and everything about it.

L4DMods.com covers everything, and I mean everything, related to the L4D community.

Leak Free is a Source engine development community started in 2004, which consists of useful tutorials and a helpful community to answer all of your level design, modeling, and programming questions. One of the most noted features is the Valve Hammer Editor Error Listing, which describes all the errors in the software and how you [...]

Left 4 Dead 411 looks like the perfect place to start if you are new to the game. It contains plenty of help for new players.

Mine-Dog.net is an established group of gamers who enjoy playing all steam games together (and some non-steam games as well). They also enjoy making comics, movies, and all other forums of media. They currently run three servers that change games monthly. All are welcome to join. Previous Design:

Mod DB is the largest website dedicated to supporting independent development of games

Mods Online is a news and community forum, with a very active user base.