Metamod:Source - A C++ Plugin Environment and Detour Library for the Source Engine.
Build instructions: See https://wiki.alliedmods.net/Building_SourceMod
Stable build snapshots: http://www.metamodsource.net/downloads.php/?branch=stable
Development build snapshots: http://www.metamodsource.net/downloads.php/?branch=master
General documentation: https://wiki.alliedmods.net/Category:Metamod:Source_Documentation
Detouring with SourceHook: https://wiki.alliedmods.net/SourceHook_Development
Development: https://wiki.alliedmods.net/Category:Metamod:Source_Development