Steal was originally just for viewing / saving Stereo lithography (STL) files, but now reads and to a lesser extent, writes a pile of different file formats.
    Steal, a quality software product, is downloadable for free for viewing STL files. It is pretty basic, because I
  haven't spent much time on it. You can zoom, pan, rotate etc. by pressing mouse buttons and dragging.

       Load / Save ASCII & Binary STL.
       Load / Save TRI format
       Load / Save OBJ format (just pulls out the polygons)
       Load / Save RAW format
       Load LWO Lightwave format (does colours)
       Load 3DS pulls out the triangles ok. (quite cool in fact (no colours))
       Load POV (pulls out triangle and smooth triangle declarations so it isn't very good)
       Load DXF (pulls out the 3dface declarations (no figures etc) so it isn't very good)
       Load NFF ok, ish
       Save VRML 1.0 (pretty basic)

    This has been superseded by Yabup, which is, surprisingly, even more versatile.

Download STeaL HERE(exe) or HERE(zip) .

STL Example Files 1, 2, 3. There are loads of 3DS and LWO files around on the web which are a whole lot cooler