Plugins can extend WordPress to do almost anything you can imagine. Below are the 10 most popular WordPress plugins.

All in One SEO Pack

Automatically optimizes your WordPress blog for Search Engines (Search Engine Optimization).

Downloaded 9,305,648 times

Jetpack by WordPress.com

Supercharge your WordPress site with powerful features previously only available to WordPress.com users.

Downloaded 725,336 times

WP Super Cache

A very fast caching engine for WordPress that produces static html files.

Downloaded 2,707,636 times

NextGEN Gallery

A full integrated Image Gallery plugin for WordPress with dozens of options and features.

Downloaded 4,306,001 times

Contact Form7

Can manage multiple contact forms, plus you can customize the form and the mail contents flexibly with simple markup.

Downloaded 5,317,392 times

Google XML Sitemaps

This plugin will generate a special XML sitemap which will help search engines to better index your blog.

Downloaded 6,620,109 times

Fast Secure Contact Form

A super customizable contact form that lets your visitors send you email. Blocks all automated spammers. No templates to mess with.

Downloads 1,984,135

Smart YouTube PRO

Smart Youtube is a professional WordPress Video plugin that allows you to easily insert videos/playlists into your post, comments and in your RSS feed.

Downloaded 1,085,658

WordPress Importer

Import posts, pages, comments, custom fields, categories, tags and more from a WordPress export file.

Downloaded 1,661,530

1 Flash Gallery

1 Flash Gallery is a Photo Gallery with slideshow function, many skins and powerfull admin to manage your image gallery without any program skills.

Downloads 737,070

 

Source: WordPress.org