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AppThemes

With the current WordPress administration area, the only way to add existing users to a certain blog is by entering their usernames, one by one. It’s very time consuming.
With this plugin, you can do it in bulk, by using the familiar “Change role to…” dropdown:
<ol>
<li>Go to WP Admin -> Users.</li>
<li>Click the “Entire Network” link.</li>
<li>Check the users you want to add.</li>
<li>Choose the new role from the dropdown.</li>
<li>Press “Change”.</li>
</ol>
Note that you have to be a super-admin to be able to do this.

User Management Tools

Allows super-admins to quickly add users to a particular blog in a multisite installation.

Newman

This plugin allows you to hide plugin update notifications for wordpress plugins that you do not want to update. 
 Once this plugin is installed and activated, a link will appear under each plugin with available updates that will allow you to block notifications for that update. Once hidden, a link will appear allowing you to unhide the notifications.
This plugin uses WordPress hooks and filters to hide the notifications.

Plugin Update Hider

This plugin allows you to hide plugin update notifications for wordpress plugins that you do…

User Management Tools vs Plugin Update Hider