Plugins can extend WordPress to do almost anything you can imagine. In the directory you can find, download, rate, and comment on all the best plugins the WordPress community has to offer.  As of writing this post today there are 24,650 WordPress plugins, 445,724,538 downloads and counting.  The most popular WordPress plugins  are matter of opinion and their relevance to your site.  WordPress users are able to tailor their site to their specific needs with needed custom functions and features without looking for a developer.

• 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.

• Akismet
  Akismet checks your comments against the Akismet web service to see if they look like spam or not.
• WooCommerce – excelling eCommerce
  WooCommerce is a powerful, extendable eCommerce plugin that helps you sell anything. Beautifully.
• Wordfence Security
  Wordfence Security is a free enterprise class security plugin that includes a firewall, virus scanning, real-time traffic with geolocation and more.
• Google XML Sitemaps
  This plugin will generate a special XML sitemap which will help search engines to better index your blog.
• Better WP Security
  The easiest, most effective way to secure WordPress. Improve the security of any WordPress site in seconds.
• WP Super Cache
  A very fast caching engine for WordPress that produces static html files.
• Advanced Custom Fields
  Fully customise WordPress edit screens with powerful fields. Boasting a professional interface and a powerfull API, it’s a must have for any web dev
• Ultimate TinyMCE
  Description: Beef up your visual tinymce editor with a plethora of advanced options.
• Really Simple CAPTCHA
  Really Simple CAPTCHA is a CAPTCHA module intended to be called from other plugins. It is originally created for my Contact Form 7 plugin.