Amelia is a powerful automated booking plugin that will help you kick-start your business and get the most tedious things off your hands.
Create self-expiring, automatic login links for your WordPress blog so you can give access to users without having them use usernames & passwords.
Block specific usernames & email addresses from automatically registering to your WordPress site. By setting up a few things, the plugin will help you maintain a clean site free of spammers who have become a problem on a daily basis.
The plugin lets you create and manage subscriptions on your site, from plans to payments and everything in between.
Make sure that guest users accessing private pages are redirected to the right place, your site's login page.
Easily manage user roles and capabilities from the WordPress dashboard in a GUI.
The only plugin I'd recommend for connecting your MailChimp account to WordPress
Add an upload form to the front-end of your site, and let users view a listing of files in any number of custom directories. Super customizable.
Supercharge the notification emails that WordPress sends out by customising them with HTML, inline CSS, and shortcodes and choose to send them to user roles or individual users.
Track the analytics of your RSS feed, and integrate with WordPress so you can redirect and customize your feeds automatically.
Use the Profile Builder plugin for WordPress to easily set up registration pages, login pages, and edit profile pages on your site's front-end with shortcodes.
A third party service which allows you to add customizable live support and chat to any WordPress site, and respond to questions on their dashboard.