Afanche Technologies, Inc.

Free
3DS Viewer is a professional app that allows you to view 3DS data files.
Free
STL Viewer 3D allows you to view ASCII and binary format STL files.
Free
3D STEP Viewer allows you to view STEP data file (.step or .stp).
Free
View, measure, analyze, transform, repair, assemble, and build 3D CAD models.
Free
Afanche3D is a professional-level 3D file viewer for Mac.