Script Download: ListUnusedContentDatabases.zip
http://gallery.technet.microsoft.com/scriptcenter/List-Unused-Content-c078e894/

This script can be used to list your unused SharePoint content databases. It can also be used to list used content databases or all content databases.

By default, we can use Get-SPContentDatabase to retrieve SharePoint content databases. But this can only list the database that’s status is Ready. The content database cannot be listed if its status is Offline.

 

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You can find more All-In-One Script Framework script samples at http://aka.ms/onescriptingallery