Régis Grison

This plugin is made mainly for french associations, because of the french 1901 law. Feel free to contact me if you think your contry have the same kind of need and I should make some adjustments for it. 
This plugin allow to handle association members by customizing the registration fields to avoid needing an additional listing. It also allows to keep track of the subscriptions. 
Note: This plugin will make use of the ACF (Advanced Custom Fields) plugin and will also contact my server to check for news about add-ons.

Law 1901 association

Handles members of an association and their subscriptions. Mainly for french associations under 1901 law.

ElbowRobo

This plugin is for BuddyPress, it adds a dashboard menu and a tab in the messages section. Once you navigate into the messages section and click the “Mass Messaging” tab you have access to all the options which you chose in the dashboard.
Including mass messaging to:
<ul>
<li>Members</li>
<li>Members of Groups</li>
<li>Members of Blogs (Sites)</li>
</ul>
And:
<ul>
<li>Select all buttons to allow mass messaging to all members easily.</li>
</ul>
In this page you also see ‘subject’ and ‘description’ just like on the Buddypress compose page.

Mass Messaging in BuddyPress

This works great for what I need, thanks a lot!

Great plugin

Ever wanted to send a message to many people at once? Now you can, introducing - Mass Messaging.

Law 1901 association vs Mass Messaging in BuddyPress