WordPress plugin directory is a great resource for free WordPress plugins. As I was browsing the repository I found 10 WordPress plugins that have the highest number of ratings and downloads.
Akismet
Akismet helps you protect against spam. Every time a comment is posted the plugin checks to if it looks like spam and automatically filters it out. You can see which comments were caught by akismet and which were spammed by a moderator.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2014-12-11.
Contact Form 7
Contact Form 7 is one of the best contact form plugins for WordPress. You can easily create multiple forms with advanced customizations. It supports ajax form submission (submit a form without refreshing the page), CAPTCHA, spam filtering (via Akismet) and so on.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-01-26.
Wordfence Security
Wordfence scans your website to see if it has been infected. The plugin compares the source code of your website to the official repository by running a deep server-side scan. The scan includes the core WordPress files, plugins and themes. Wordfence is also known to make your site faster.
This plugin is actively installed on over 700,000 websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-01-26.
All in One SEO Pack
All in One SEO Pack optimizes your website for SEO (Search Engine Optimization). It includes support for sitemap, Google Analytics, canonical URLs, page navigation, e-commerce integration, nonce security, meta tags, duplicate content and so on. It also optimizes title and meta description.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-01-30.
Jetpack
Jetpack makes some powerful wordpress.com features available to you. It includes CSS customizations, Carousels, contact forms, tiled galleries, mobile theme and tools like shortcode embeds, VideoPress, social sharing, post by email, subscription, site verification and so on.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-02-19.
WordPress SEO
WordPress SEO plugin helps you optimize your website for SEO. It has a great page analysis tool which allows you to analyse your content for better SEO. It includes support for meta elements, XML sitemaps, breadcrumbs, RSS feed, social sharing, import and export, WordPress multi-site compatibility and so on. It also includes support news websites.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-02-23.
Google Analytics
This plugin enables Google Analytics tracking on your website. It supports universal tracking, demographics and interest reporting, outbound links and downloads tracking, pageviews and events tracking and so on.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-02-18.
WooCommerce
WooCommerce is one of the best e-commerce plugins for WordPress. It turns your website into a powerful store and helps you sell anything. It provides advanced customizations with tons of payment gateways to accept payments globally.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-02-20.
iThemes Security
iThemes Security, formerly known as Better WP Security, is a security plugin for WordPress. It protects your website by detecting security holes and plugin vulnerabilities. Some of the features include 2-factor authentication, malware scanning, GeoIP banning, file comparison, wp-cli integration and so on.
This plugin is actively installed on over 600,000 websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2015-03-02.
WordPress Importer
WordPress Importer is a great tool to import content from a WordPress export file. It allows you to import posts, pages, custom post types, comments, custom fields, post meta, categories, tags and so on.
This plugin is actively installed on over a million websites. It is compatible with the latest version of WordPress (4.1) and was last updated on 2014-10-16.