Top Websites for source engine

sbox.game

A sandbox game development platform by Facepunch Studios.

garry-s-mod.ru

Addons, maps, and content for the Garry's Mod game.

sourcemod.net

Write modifications for Half-Life 2 with a scripting languag...

twhl.info

Half-Life and Source mapping tutorials and resources.

momentum-mod.org

A free, standalone platformer built on the Source Engine.

interlopers.net

Half-Life 2 Tutorials, News & Source related content

srcds.com

Host and manage online games in a virtual environment.

obsidianconflict.net

A free, non-profit Half-Life 2 modification.

sourceop.com

A platform for Half-Life 2 plugin development and discussion...