[All plugins] Is there a way to tell which plugins are/are not being used in a MultiSite?

Is there a way to tell which plugins are or are not being used in a MultiSite? We currently have over 100 plugins installed and I'm SURE some of them were only installed for testing purposes. I'd like to clean things up, but short of going through each and every subsite, I don't know of a way to tell what plugins are being used on the network or not.