Jetpack - Jetpack offers SEO and security plugins for Wordpress.
HootSuite - Enhance your social media management with Hootsuite, the leading social media dashboard. Manage multiple networks and profiles and measure your campaign results.
WP User Manager - The most customizable profiles, community builder and membership WordPress plugin
SproutSocial - Sprout Social is a social media management tool created to help businesses find new customers & grow their social media presence. Try it for free.
UpStream Plugin - UpStream Plugin is a free-to-use project management plugin that allows you to manage various types of projects right from your WordPress site.
Buffer - Buffer makes it super easy to share any page you're reading. Keep your Buffer topped up and we automagically share them for you through the day.