From Frank Midgley, "I tried running osgconv --formats yesterday on OS X and got no results. Turns out the changes discussed in the "osgDB::listAllAvailablePlugins win32 fix" thread back in Sep '08 broke this. The OSG_PLUGIN_EXTENSION macro is being defined in src/osgDB/CMakeLists.txt from CMAKE_SHARED_LIBRARY_SUFFIX which is "dylib" on OS X. The problem is that all of the plug-ins are setup in OsgMacroUtils?.cmake with:
which gives them .so extensions. Since ".so" != ".dylib" osgDB::listAllAvailablePlugins finds no plug-ins. I believe the correct solution is to use CMAKE_SHARED_MODULE_SUFFIX instead. This builds and runs correctly on OS X but I have not tested on other platforms.
Attached is an updated src/osgDB/CMakeLists.txt based on rev 9915. The change is at line 108. To validate: build and then run bin/osgconv --formats. You should get many screenfuls of plug-in features, extensions and options."