IGES/IGS is a common ASCII CAD format and most of the modern CAD programs support it and can export their CAD drawings to it. In case of DWG it should be very easy, considering DWG is de facto standard in CAD industry and it can be imported/opened in almost any CAD software.
Open DWG file Open IGS fileA CAD viewer program with conversion capabilities
A CAD and Gerber conversion software
A set of 3D modeling tools
A 3D modelling software
3D CAD/CAM tool for product development
A CAD converter with huge format support
A dedicated 2D/3D CAD software
A 3D CAD translation software
A suite of CAD applications