Smush Image Compression and Optimization
Easily and losslessly optimize your WordPress images automatically. Everything works in the background, so there's very little set up.
WP User Frontend Pro
Build forms so that users can edit posts and user profiles from your WordPress site's frontend, support for login and registration too.
Voice Search
Add a microphone icon to your search form which allows users to use their devices microphone in speech activated search.
WP-Sweep
Clean up and optimize your database by removing unused metadata, post revisions, and leftover data from plugins, among other things.
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
