Modeling Programs:

• Blender
• 3D Studio Max
• Maya
• fragMOTION
• kHED
• Milkshape 3D

SMD, DMX, VTA Exporter Plugins:

• Blender SMD Tools
• Game Zombie SMD Tools (3dsmax)
• Wall Worm Model Tools (3dsmax)
• Wunderboy's SMD plugins (3dsmax)
• MAYA MESA

Compile Tools

• Studiomdl.exe
• Crowbar Tool: GUI wrapper, Compiler, Decompiler and Unpacker

Miscellaneous

• Qc_eyes.exe
• Half Life Model Viewer
• QC Commands

Note: Valve has released some of their complete models with the source SDK. Look in C:\Program Files (x86)\Steam\steamapps\*accountname*\sourcesdk_content before decompiling certain models.

Decompiling Tools

• Crowbar Tool: GUI wrapper, Compiler, Decompiler and Unpacker