STL Exporters for SketchUp

I had a couple recent comments asking about exporting STL files from SketchUp. I know of 3 plug-ins that can export .stl files.

• CADSpan - provides several 3D printing tools in addition to .stl exporting.
• Guitar Lists's DXF/STL Exporter
  
• Dider Bur's STL Exporter. Search for "stl" on the page.
  

I have not had a need to try any of these yet and so I can not offer any comment on how well they work.