Affiliazione WP Affiliates plugin allows you to set up an affiliate marketing program for your users tracking their referrals, clicks and sales
Automessage WordPress Plugin allows you to send custom automated welcome emails for several days after a user joins your site or network.
E-Newsletter plugin adds a professional management system for your email newsletter and subscribers to your WordPress website
Invite Plugin allows your users to send out invitations to friends to view or join your WordPress site.
The Private Messaging WordP ress plugin from WPMUDEV allows your users to chat and share files safely on your website through direct messages.
Social Marketing share
Social Marketing plugin allows you to offer incentives for users sharing your products or services on Facebook, Twitter, Google+ or LinkedIn.
Subscribe by email
Subscribe by Email Plugin allows your visitors to be automatically notified about your latest content in email digests
Ultimate Facebook integration
Ultimate Facebook plugin fully integrates your WordPress blog with Facebook (autopost to your Facebook page or wall
Simple Ads WordPress Plugin allows you to insert ads on posts and pages across a multisite network
Popup pro plugin allows you to add highly flexible and customizable popups for advertising or special promotions to your site
The Easygram WordPress Plugin allows you to create amazing posts or galleries on your WordPress Site which include your Instagram photos
The Social Commerce WordPress Plugin converts your WordPress Site into a Facebook friendly destination - especially for your social eCommerce customers