Popslide
Easily add a simple message to the top or bottom of your page that only slides in when a user is on your site for a set period of time.
BackupBuddy
Back up, restore, migrate, and give yourself peace of mind. Use this plugin to schedule backups, store them in the cloud, and restore from them at any time.
Private Content Login Redirect
Make sure that guest users accessing private pages are redirected to the right place, your site's login page.
wpDataTables
Allows you to upload data from a CSV, Excel, or even a serialized array, and produces a fully responsive data table for your WordPress site.
Stop Emails
Automatically suspend outgoing emails on your WordPress install, and optionally log emails for debugging.
User Role Editor
Easily manage user roles and capabilities from the WordPress dashboard in a GUI.
MailChimp for WordPress
The only plugin I'd recommend for connecting your MailChimp account to WordPress
File Away
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.
Soliloquy: Responsive Slider
A responsive slider built for speed and flexibility. Create your sliders in the back-end, customize to your heart's content, and then embed them anywhere on your site.
CFS Custom Category Fields WordPress Plugin Review
Add custom fields using Custom Field Suite to categories and taxonomies with ease.
Sprout Invoices
Easily set up estimates and create Invoices for your clients right in the WordPress dashboard. A complete project management solution.
After Post Manager
Add a short byline or message at the end of the post and use shortcodes to populate dynamic fields.