Shawn

Say goodbye to the headache of managing users in a multisite network! Now when a user visits a blog in the network, the user will be added to the blog with your specified roles automatically.
Here is how this plugin works:
<ol>
<li>When a user visits a site, this plugin checks if the user is already a member of the site.</li>
<li>If the user is a member, do nothing.</li>
<li>Otherwise add the user to the site with the user\’s role in blog #1, or a role specified by you. [Sync Role]</li>
<li>If the user is not an existing member of blog #1, the user will be added with a role specified by you. [Default Role]</li>
<li>When a user\’s role is updated, the user\’s new role can be updated across all the bogs the user is member of. [Role Update]</li>
</ol>

Multisite User Role Sync

Automatically add users to peer blogs in a multisite network.

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I spent about 30 minutes looking at different multisite user management plugins and all of them were either out of date, or tried to do too much.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

Multisite User Role Sync vs Multisite User Role Manager