Charles Fulton

This plugin suppresses features of the Multisite site creation process:
<ul>
<li>It suppresses the welcome email sent to new site administrators on site creation</li>
<li>It cancels the site creation process if the given email does not exist, instead of creating a local user</li>
</ul>
It also flushes rewrite rules on site creation to address https://core.trac.wordpress.org/ticket/20171.
<h3>Privacy</h3>
This plugin neither collects nor stores any personal, private, or identifying information about any user.

Site Creation Utilities

This plugin improves the Multisite site creation process by eliminating undesired features.

3dperuna

WPMU has great themes and plugins. Unfortunately, many, if not most, come with a nag notice that admins see about installing their notifications dashboard plugin. If you’ve bought one plugin for your site this is probably overkill. If you’re a developer you don’t need this on your client’s sites.
This is a simple plugin that removes the notice. The 1.3 version has been checked against WP 4.4 and recent WPMU plugins, but still should be backwards compatible with older versions of WPMU plugins.
Note: If you do decide to you install the WPMU notifications plugin, please deactivate this one first. Errors may occur if you don’t.
If you like this plugin consider donating: http://www.protospace.com/wpmu-no-nag-plugin/

Remove WPMU Dashboard Install Nag

Works as advertised. Now, why a plugin should be needed for this is another question altogether, and installing and activating this plugin is no substitute for filing an RFE to either add a close button to those annoying nags or a switch to turn them off (and their pref doesn't always work, apparently).
Thanks for this!



Simple and to the point

This plugin removes the nag notice at the top of WPMU plugins and themes.

Site Creation Utilities vs Remove WPMU Dashboard Install Nag