Nem's Tools
GCFScape
FreePowerful archive extractor for Valve packages
Windows
VTFLib
FreeHave a library for LGPL open source programming.
Windows
Crafty
FreeBrowse 3D objects, material, model and files.
WindowsMAP Viewer
FreeMAP Viewer: Fast 3D .MAP File Previews
WindowsBatch Compiler
FreeBatch Compiler: Streamline Your Map Compilation
WindowsTerrain Generator
FreeNem's Mega 3D Terrain: Ultimate Control for Game Developers
Windows