There’s always a lot of discussion on the WPMU DEV forums about this very topic, so I asked our support crew and developers what plugins they recommend people install on their network.
Whether you’re new to running a Multisite network or have been hosting your own network for some time, you’re sure to find many of the plugins below (in no particularly order) useful for managing your sites.
via 25 Must-Have Plugins for WordPress Multisite Networks – WPMU DEV.
If you’re running a multisite WordPress install this list of plugins is a pretty good place to start in the search for the right mix of features to run the network smoothly and provide useful options to your bloggers. We use many of these plugins on Classcaster, the free podcasting and blogging network for CALI members.