There's a new program called CADExchanger at http://www.cadexchanger.com/
, currently free in beta release, although I don't know what their commercial ambitions are. It's a viewer/converter for IGES, STEP, BREP (OpenCascade native format), STL and VRML. They're also planning and working on ACIS SAT and Parasolid X_T conversion. Even at this early stage, it's a really nice viewer and a few tests that I've done have had reliable conversion to STL performed. Although stl binary format has hiccups, ASCII stl works well.