Best Plugins for Backup and Optimization
W3 Total Cache
Easy Web Performance Optimization (WPO) using caching: browser, page, object, database, minify and content delivery network support.
WP Super Cache
A very fast caching engine for WordPress that produces static html files.
WP-DBManager
Manages your WordPress database.
Duplicator
Duplicate, clone, backup, move and transfer an entire site from one location to another.
UpdraftPlus Backup and Restoration for WordPress
Backup and restoration made easy. Complete backups; manual or scheduled (backup to S3, Dropbox, Google Drive, Rackspace, FTP, SFTP, email + others).
WP Optimize
This simple but effective plugin allows you to clean up your WordPress database and optimize it without phpMyAdmin.
WP Migrate DB
Exports your database, does a find and replace on URLs and file paths, then allows you to save it to your computer.
WordPress Database Reset
A secure and easy way to reinitialize the WordPress database to its default settings.
Best Plugins for SEO
WordPress SEO by Yoast
Improve your WordPress SEO: Write better content and have a fully optimized WordPress site using the WordPress SEO plugin by Yoast.
All in One SEO Pack
WordPress SEO plugin to automatically optimize your WordPress blog for Search Engines.
Google Analytics for WordPress
Track your WordPress site easily and with lots of metadata: views per author & category, automatic tracking of outbound clicks and page views.
SEO Friendly Images
Adds ALT and TITLE meta tags to your images so you can start getting valuable Google Images traffic.
Best Plugins for Security
BulletProof Security
WordPress Website Security Protection: Effective…Reliable…Easy to use
Better WP Security
The easiest, most effective way to secure WordPress. Improve the security of any WordPress site in seconds.
Wordfence Security
Wordfence Security is a free enterprise class security plugin that includes a firewall, virus scanning, real-time traffic with geolocation and more.
Core Functionality
Jetpack by WordPress.com
Supercharge your WordPress site with powerful features previously only available to WordPress.com users.
Contact Form 7
Just another contact form plugin. Simple but flexible.
Grunion Contact Form
Add a contact form to any post, page or text widget. Messages will be sent to any email address you choose. As seen on WordPress.com.
http://wordpress.org/plugins/si-contact-form/
A super customizable contact form that lets your visitors send you email. Blocks all automated spammers. No templates to mess with.
Crayon Syntax Highlighter
Syntax Highlighter supporting multiple languages, themes, fonts, highlighting from a URL, local file or post text.
Duplicate Post
Clone posts and pages.
WPML – $80
Running a multilingual site with multiple translators is an incredibly difficult task; this plugin is absolutely essential if you plan on doing so in WordPress. No other multilingual plugins come close ? but this comes at a price of $80 for the full version.
WordPress Language
Run localized WordPress sites easily. Select the language and everything else happens automatically.
Custom Taxonomy Sort
Custom Taxonomy Sort allows you to explicitly control the sort order of all taxonomy terms.
Category Order and Taxonomy Terms Order
Order Categories and all custom taxonomies terms and child terms using a Drag and Drop Sortable javascript capability. No Theme update is required.
Category Sticky Post
Mark a post to be placed at the top of a specified category archive. It’s sticky posts specifically for categories.
Tag Sticky Post
Mark a post to be placed at the top of a specified tag archive. It’s sticky posts specifically for tags.
Velvet Blues Update URLs
Updates all URLs and content links in your website.
WooSidebars
WooSidebars adds functionality to display different widgets in a sidebar, according to a context (for example, a specific page or a category).
Page Links To
Lets you make a WordPress page (or other content type) link to an external URL of your choosing, instead of its WordPress URL.
SearchWP Live Ajax Search
Template powered live search for any WordPress theme. Does not require SearchWP, but will utilize it if available.
Plugins for Mail and Newsletter
WYSIJA Newsletters
Send newsletters, post notifications or autoresponders from WordPress easily, and beautifully.
WP Mail SMTP
Reconfigures the wp_mail() function to use SMTP instead of mail() and creates an options page to manage the settings.
Plugins for Under construction
Ultimate Coming Soon Page
Creates a Coming Soon page or Launch page for your Website while it’s under construction and collects emails from your visitors.
WP Maintenance Mode
Adds a splash page to your site that lets visitors know your site is down for maintenance. Full access to the back- & front-end is optional.
Maintenance Mode
A coming soon plugin that enables you to inform your users when your new website is going to be live while you are working on building it
Countdown Timer
This plugin allows you to setup a series of dates to count to or from in terms of years, months, weeks, days, hours, minutes, and/or seconds.
Plugins for Social sharing
Slick Social Share Buttons
Slick social share buttons adds facebook, twitter, google +1, linkedin, digg, delicious, reddit, stumbleupon, buffer and pinterest pin it social media
WP Facebook Open Graph protocol
Adds proper Facebook Open Graph Meta tags and values to your site so when links are shared it looks awesome!
Simple Follow Me Social Buttons Widget
Add follow me social buttons. Uses font icons, ready for Retina Display.
Plugins for managing users and their access
Members
A user, role, and content management plugin that makes WordPress a more powerful CMS.
Capability Manager Enhanced
A simple way to manage WordPress roles and capabilities.
Map Cap
Control who can publish, edit and delete custom post types. Silly name, useful code.
Adminimize
Adminimize is a WordPress plugin that lets you hide ‘unnecessary’ items from the WordPress backend and many many more …
Ajax Login & Register
Allows you to create a custom login and registration page or login and registration modals. Complete with AJAX verification and Facebook login support
Simple Local Avatars
Adds an avatar upload field to user profiles. Generates requested sizes on demand just like Gravatar!
UserPro – User Profiles with Social Login?($28)
It?is a full featured user profile and community plugin for WordPress which offers beautiful front-end profiles, login and registration for WordPress
Plugins for improving interactivity
JQuery Accordion Menu Widget
Creates vertical accordion menus from any WordPress custom menu using jQuery. Add menus using either widgets or shortcodes.
Plugins for Popup and notifications
WPFront Notification Bar
Easily lets you create a bar on top or bottom to display a notification.