lakrisgubben

This plugin uses BuddyPress’s notification system to let users subscribe to all new posts on a site (or many sites if you run Multisite). When a new post is published all users subscribed to the site gets a notification and optionally an email (can be turned off in their BuddyPress email settings).
<h4>Requires</h4>
<ul>
<li>BuddyPress 2.3 or later</li>
<li>WordPress 4.3 or later</li>
</ul>

BP Site Subscriber

This plugin uses BuddyPress's notification system to let users subscribe to all new posts on a site (or many sites if you run Multisite).

hardlyneutral

This plugin is built to display BuddyPress groups on the new user registration page. Groups can be displayed as:
<ul>
<li>a list of checkboxes</li>
<li>a list of checkboxes in a scrollable container</li>
<li>a list of radio buttons</li>
</ul>
New users will automatically join any of the groups selected during the registration process.
Options are available in the admin area to configure the title of the groups list on the registration page, the 
description of the groups list, whether private groups are visible to new users, the order in which groups are 
displayed, and how many groups will be visible.
<h3>Custom Styles</h3>
This plugin includes specific CSS for changing the way content is displayed. The default CSS will place the group after the “Profile Details” section and before the “Complete Sign Up” button on the register page. You can view <code>includes/styles.css</code> in this plugin directory to see how to target each element.
Here is a list of the current selectors used in <code>includes/styles.css</code>.
Groups section:
<pre><code>#registration-groups-section {
 float: right;
 width: 48%;
}
</code></pre>
Checkboxes:
<pre><code>.reg_groups_group_checkbox {
 margin: 0 5px 0 0;
}
</code></pre>
Form labels:
<pre><code>#buddypress .standard-form label.reg_groups_group_label,
.reg_groups_group_label {
 display: inline;
 font-weight: normal;
}
</code></pre>
Groups section – responsive:
<pre><code>@media only screen and (max-width: 480px) {
 #registration-groups-section {
 float: none;
 width: 100%;
 }
}
</code></pre>
List items:
<pre><code>.reg_groups_item {
 list-style: none;
}
</code></pre>
No groups message:
<pre><code>.reg_groups_none {
 font-style: italic;
 color: gray;
}
</code></pre>
Multiselect:
<pre><code>.reg_groups_list_multiselect {
 height: 8em;
 border: 1px solid #ccc;
 background: #fafafa;
 padding: 6px;
 overflow: auto;
}
</code></pre>

BuddyPress Registration Groups

Allows a new BuddyPress user to select groups to join during the registration process.

BP Site Subscriber vs BuddyPress Registration Groups