Maxaud

(NOTE: Before saying this plugin is broken, please understand what this plugin does. It’s meant for WordPress installs that have multiple NETWORKS.)
Adds the ability to have different themes available to different NETWORKS in a multisite atmoshpere.
WordPress allows for multiple “networks”, these are not to be confused with sites. A network holds blogs underneath of it.
This plugin will allow you to separate themes into different directories so they’re only accessable and viewable to the networks you choose.
The plugin will attempt to create a directory in the /wp-content/ directory named /ms-themes/. If it fails to create it, then you will need to make one.
In the /ms-themes/ directory you will create a folder for each network that you want to allow only certain themes to.
Example: 
If you have a theme named “Snarfer Theme”, and you want to only allow it to be viewable/available to the network (and all sites on that network) with the site_id of 7, you would place the snarfer theme directory in /wp-content/ms-themes/7/
Future releases:
<ul>
<li>Network option to turn off auto creation on/off network directories, index.php files.</li>
<li>Network option to display network ID in the footer of sites so network admins can easily tell what network a site is under.</li>
</ul>

Multisite Themes

Adds the ability to have different themes available to different NETWORKS in a multisite atmoshpere.

Pippin Williamson

Adds an “Add New” sub menu item to the Plugins menu of all sites inside of a network for network admins.

Multi Site Plugins Add New

The lack of Plugins > Add New link was driving me totally nuts. This plugin does exactly as advertised and keeps me sane. ^_^

Simple fix makes a big difference

I love having this shortcut in my Multisites!

This plugin keeps thigs simple and only tries to do one thing, I wish all plugins were the same but unfortunately most users (and plugin authors) don´t understand that often less is more.

Good simple plugin

Adds an "Add New" sub menu item to the Plugins menu of all sites inside of a network for network admins.

Multisite Themes vs Multi Site Plugins Add New