DXF to OpenGL  
   This program reads a 3D graphics image file, in the DXF data format, and displays it using OpenGL.
   http://www.bearcave.com/dxf/dxfintro.htm

AutoCAD DXF Documentation  
   Technical information about DXF from its creators Autodesk. This DXF Reference is available for online viewing, or it can be downloaded as a WinHelp file, or a zipped set of HTML files.
   http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=2882295&linkID=2475323

DXF2rad  
   A converter to translate 3D DXF data to the Radiance scene file format, available for multiple platforms.
   http://www.schorsch.com/download/dxf2rad/

DWG DXF Convert  
   An AutoCAD DWG/DXF bi-directional translator built using the powerful DWGDXFLib library. It converts an AutoCAD DWG file into an AutoCAD DXF file and vice-versa without the need of AutoCAD. DWG DXF Convert also supports batch conversions of multiple DWG o
   http://www.fpsols.com/dwg_dxf_convert.html