Nem's Tools
GCFScape
FreePowerful archive extractor for Valve packages
Windows
VTFLib
FreeHave a library for LGPL open source programming.
Windows
Terrain Generator
FreeGenerate terrain with complete 3D control.
WindowsCrafty
FreeBrowse 3D objects, material, model and files.
WindowsBatch Compiler
FreeBatch Compiler: Streamline Your Map Compilation
WindowsMAP Viewer
FreeMAP Viewer: Fast 3D .MAP File Previews
Windows