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Multisite Directory provides a customizable Network-wide site directory for WordPress Multisite installations. You can categorize subsites in your Network, add full-length descriptions and featured images to them, and more. Theme developers can customize the look and feel of the site directory using all the tools they’re already familiar with. Blog authors can use a highly-configurable shortcode (<code>[site-directory]</code>) to display the directory anywhere shortcodes are supported.
Each time a new site or blog is added to your Network, a corresponding entry in the site directory is added, too. The directory is managed from the Network’s main site, but most changes to the subsites (other blogs) automatically update the directory. Many parts of a given site’s appearance in the directory can be modified without affecting the site itself. This means a Super Admin can use a custom site logo, tagline, and so on in the directory itself, without changing the site’s actual logo, tagline, and so on. Additional options in the Network Settings → Network Directory section allows Super Admins to tweak the bells and whisltes, such as keeping Directory Entry titles in sync with Site Name changes.
Site directory entries are implemented as a hierarchical custom post type in the main site. These pages can be categorized with a custom <code>subsite_category</code> taxonomy. We’ve found that this combination allows maximum flexibility while providing the tightest integration with existing WordPress core features. As a result, no new tables are added to your install, and no side effects are introduced. It Just Works.(TM)
Quickstart guide
After <a href="https://wordpress.org/plugins/multisite-directory/installation/" rel="ugc">installing</a> the plugin, you’ll want to:
<ol>
<li>As a Super Admin, go to My Sites → Network Admin → Sites. Notice the new “Categories” link on the sidebar.</li>
<li>Create some categories! If the category relates to a location (maybe it’s a site for a regional chapter of your organization?), be sure to click the map to geotag it.</li>
<li>Click on “Directory,” immediately above “Categories.” These pages are the individual directory entries, not the blogs. Categorize these pages as you would regular WordPress Pages to organize your Site Directory.</li>
<li>Go to any site’s Appearance → Widgets screen, and add a “Network Directory Widget” to a widget area.</li>
<li>If you’ve geotagged some of your Site Categories, choose “Display as map” from the widget options. (Otherwise, leave it on “Display as list.”)</li>
<li>Click Save, view your blog, and enjoy your new Site Directory!</li>
</ol>
Check out the <a href="https://wordpress.org/plugins/multisite-directory/screenshots/" rel="ugc">Screenshots</a> for a few examples. 
This plugin provides a number of functions to Theme authors so that they can make use of the Multisite Network Directory features in their themes. This section documents those functions. For implementation details, see this plugin’s <code>includes/functions.php</code> file.
<h4>get_site_directory_terms</h4>
Gets all categories in the site directory.
<ul>
<li>@return array|false|WP_Error</li>
</ul>
<h4>Get site terms</h4>
Gets the categories assigned to a given blog in the network directory.
<ul>
<li>@param int $blog_id</li>
<li>@return array|false|WP_Error</li>
</ul>
<h4>the_site_directory_logo</h4>
Prints the site’s custom logo or the site directory entry’s featured image, if it has one.
<ul>
<li>@param int $blog_id Optional. The ID of the site whose logo to get. Default is the current directory entry’s site’s logo.</li>
<li>@param string|int[] $size</li>
<li>@param string|string[] $attr</li>
<li>@return void</li>
</ul>

Multisite Directory

Add a browseable, flexible directory of the sites in a WP Multisite network. Each subsite gets its own page.

Daniel Westermann-Clark

By default, WordPress network usernames cannot contain anything but lowercase letters and numbers. This plugin adds network options to let you include hyphens, underscores, or uppercase letters, if desired.
Furthermore, this plugin gives you the option to allow email addresses as usernames, or to allow all-numeric usernames (e.g. “1234”).
Finally, this plugin lets you override the minimum length for usernames (which defaults to four characters).
To follow updates to this plugin, visit:
https://danieltwc.com/
For help with this version, visit:
https://danieltwc.com/2011/network-username-restrictions-override-1-0/

Network Username Restrictions Override

Does what it says!

Override restrictions on WordPress network usernames.

Multisite Directory vs Network Username Restrictions Override