Roy Tanck

This plugin will help you:
<ol>
<li>Find plugins and themes that are not active on any blog.</li>
<li>Determine the impact in case a theme/plugin needs to be upgraded, removed or reconfigured.</li>
<li>See if a widget is in use on any blogs, and track down where.</li>
<li>Find users who do not have a role on any site (and are not network administrators).</li>
</ol>
This plugin currently does nothing on single-site WordPress installs.

Network Admin Assistant

Helps you manage a WordPress network by displaying useful statistics.

David Gewirtz

adiant

Beyond what the name implies, the Reveal Network Activated Plugins plugin can display all Plugins that WordPress would normally hide: WordPress only displays Network Activated and Must-Use plugins, as well as Drop-ins, on the Installed Plugins Network Admin panel; even there, they can be easily missed. Under the control of any Super Administrator, Reveal Network Activated Plugins allows Network Activated and Must-Use plugins, and Drop-ins, to be displayed on each site’s Installed Plugins Admin panel, with “Network Activated”, “Must-Use Plugin” or “Drop-in” displayed below the plugin name where “Activate” or “Deactivate” is displayed for other plugins. In addition, the plugin’s Network Admin panel, available only to Super Administrators, and the Delete Plugins panel, show which Plugins are activated on which Sites within the WordPress Network.
In a WordPress Network, i.e. – a single WordPress installation that provides multiple sites (“Multi-site”), Plugins can be activated on one or more individual sites or they can be Network Activated, which means they are activated on all sites. In addition, Must-Use plugins are automatially activated if present and Drop-ins are activated Network-wide by a Constant set in wp-config.php. Confusion can result because WordPress does not display any of these plugins on each site’s Installed Plugins Admin panel, a confusion that this plugin hopes to eliminate.
A warning Notice is displayed if this plugin is activated on a WordPress installation that is not (yet) a WordPress Network.
Every effort has been made to not interfere with plugins that create or modify their own entry on the Installed Plugins Admin panel.
<h4>Settings</h4>
A Settings page for this plugin is available to Super Administrators on both the Plugins and Settings submenus within the Network Administration panels. It determines which plugins are visible on the Plugins Admin panel of each site within the Network.
A “Who Sees Them?” table of choices can be used to set who sees Network-Activated and Must-Use plugins, and Drop-ins. It can even be used to hide any or all of them from everyone.
The Plugins row of the table actually controls the same Setting as the “Enable administration menus – Plugins” checkbox at the bottom of the Network Settings Admin panel. It is provided here to avoid the confusion that otherwise exists when Super Administrators cannot figure out why their Site Administrators do not even have a Plugin menu on their Site Admin panels.
Within the “Who Sees Them?” table, the column entitled “Site Administrators” also refers to anyone else with the “activate_plugins” Capability for the Site.
A “Show/Hide Plugins” table of choices can be used to always Display or Hide specific plugins for Site Administrators. This is especially useful for Super Administrators developing or testing new plugins that are not yet ready for use by Site Administrators. It can be also used when only a few of the many plugins installed are to be made available to Site Administrators.
<h4>Definitions</h4>
Super Administrator – controls the Network (multi-site) settings and setup, as well as settings and setup for all individual Sites within the Network, through access to all Admin panels for the Network and all Sites.
Site Administrator – has no access to Network settings and setup, but does have access to Admin panels for any Site for which he has the Role of Administrator.
“activate_plugins” Capability – one of many settings for a User for a specific Site, i.e. – each User either has or does not have the “activate_plugins” Capability for a given Site. Anyone with the Role of Administrator for a Site automatically has the “activate_plugins” Capability and it cannot be removed. However, it can be disabled through the “Enable administration menus – Plugins” Network setting described above.

Reveal Network Activated Plugins

Displays Network-Activated and Must-Use (MU) plugins, and Drop-ins on the Installed Plugins Admin panel for individual sites of a WordPress Network.

Network Admin Assistant vs Reveal Network Activated Plugins