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.

kebes

VEO Multisite Plugin Manager allows you to: 
– View which plugins are active globally. 
– See the sites where plugins are individually active. 
– Quickly navigate to the plugin pages of specific sites.

VEO Multisite Plugin Manager

Manage and monitor plugin activation across WordPress Multisite networks.

Network Admin Assistant vs VEO Multisite Plugin Manager