Many CAD programs support both the IGES (.igs, .iges) and STL format (for 3D printing) and thus can translate the data from one format to another and perform igs to stl conversion. In most cases this is done for 3D printing purposes - Stereo-lithography.
Open IGS file Open STL fileA website STL converter
A CAD and Gerber conversion software
A Mac version of the popular 3D visualisation software
A set of 3D modeling tools
A converter for 3D formats
An online CAD conversion service
A CAD converter with huge format support
A CAD/CAM for material working industry
A CAD visualizaton, analyzation and translating system
An open source multiplatform 3D CAD/MCAD/CAx/CAE/PLM modeler
A dedicated 2D/3D CAD software
A commercial online CAD converter
A 3D CAD translation software
A dedicated CAD converter
A CAD drawing and CNC programming system