I want a setup like this:
+- /ApplicationFolder
-- App.exe
-- Core.dll
-- AnotherShared.dll
+- /PluginsFolder
-- plugin1.dll
-- plugin2.dll
<
My MEF application is set up so that plugin projects compile to their own folder (as the is the default), then I use a post-build command to copy specific files to the output extensions folder.
The other way is to have the project build directly into the appropriate output folder and, as the other poster said, open the "Properties" panel for each relevant reference in your plugin project and set "Copy Local" to false.