Konstantin Obenland

This plugin lets you as a network administrator add users to your sites without having to remember or look up the user’s login name. It replaces the input field with a comfortable dropdown menu, so you can choose between all existing users that are not yet added to the site.
Don’t worry about code overhead or performance issues, the plugin will only be loaded when a network admin screen is requested.

WPMU Network Site Users Dropdown

Replace the input field for adding existing users to a site with a more comfortable dropdown menu!

r-a-y

This plugin makes things a little easier for network administrators managing their network plugins.
How so? Glad you asked! Active network plugins are separated from inactive ones on the WordPress network plugins page.
Need a visual? Check out <a href="http://i46.tinypic.com/6gv32g.png" rel="nofollow ugc">this screenshot</a>.
For WP 3.1+, if you’re on a regular admin plugins page, you’ll see a small blurb with an easy, direct link to your network plugins page.
If you’re not using <a href="https://codex.wordpress.org/Create_A_Network" rel="nofollow ugc">network mode</a>, you don’t need this plugin.
<h3>Recommendations</h3>
Check out the companion plugin, <a href="https://wordpress.org/extend/plugins/green-active-plugins/" rel="ugc">Green Active Plugins!</a>.
They go well together like coffee and doughnuts!

Blue Network Plugins!

Separates active network plugins from inactive ones on the Wordpress network plugins page. Requires Wordpress Multisite.

WPMU Network Site Users Dropdown vs Blue Network Plugins!