gregsurname

This WPMU plugin creates under the Site Admin menu called “Bulk Create Blogs” where you can bulk create/add users to blogs.
To use the plugin you must create correctly formatted data. The plugin takes 
CSV formatted data where each row contains the following data.
<pre><code>domain, user_id, blog_title, blog_topic,
</code></pre>
Each of these fields is described below.
<ul>
<li>blog_domain (Mandatory): the domain name of the blog, this should only contain alphanumeric characters and be in all lowercase. If the blog domain is empty then users will be added to the site’s root blog.</li>
<li>user_name (Mandatory): the login id of the user to be added to the blog.</li>
<li>blog_title (Optional): the title of the blog.</li>
<li>blog_topic (Optional): the name of the blog topic that this blog will be categorised under. These topics are setup under the ‘Blog Topic Management’ tab. A blog_title must be chosen if you wish to set the blog topic. (Requires cets_blog_topics plugin.) </li>
</ul>
When each line is processed, if the blog named already exists then the user given 
is added to the blog. If the blog does not exist then it is created. If a blog title 
is not provided then the blog domain is used.
This plugin also provides support for LDAP user creation. If a user does not exist and 
the ldap_auth plugin is installed then it will attempt to create a new user.
At the moment this plugin only supports sites that use domain blog naming. Support for 
sub-directories is not planned but you could easily add it yourself.
The number of blogs that can be imported at a time is limited.

Bulk Create Blogs

A WPMU plugin for allowing the site admin to bulk create blogs using CSV data.

OzTheGreat

For WordPress Multisite (WPMU) installs, allows Super Admins to easily manage each users roles and blogs from one 
screen in the Network Admin menu.
You no longer have to go to each blog to change the user’s role. It’s also 
much easier to see which sites a user is associated with.

Multisite User Role Manager

Ajax management makes it super easy to add users to a bunch of sites in the network. Does 1 things really well, more plugins should work like this.

Great for multisite user management

Made adding a user to 20 sites a lot easier than using WP's default interface for that (way less clicking around).

Much easier to assign a user to many sites

I spent about 30 minutes looking at different multisite user management plugins and all of them were either out of date, or tried to do too much. This plugin solved the exact issue I was dealing with: adding a user (with a specified role) to all of my client's subsites. 

Thank you very much. 

I wish you all the best,
Kevin.

P.S. the CSS for the admin screen where you add users to subsites was a bit off for me (in Chrome). The table did not fit the modal background (it hung off to the right a bit, and forced me to scroll even though there was plenty of vertical space). It doesn't bother me but it might bother some other users so I figured I would let you know. 

Excellent plugin - it does what it says!

Manage user roles for each blog from a single screen on multisite (WPMU) setups

Bulk Create Blogs vs Multisite User Role Manager