Popular WordPress Plugins by Category

Administrative Plugins

1. 404 Notifier, Email notification for all 404 errors on your WordPress site.
2. Advertising Manager, Manages and rotate your Google Adsense and other ads on your WordPress blog or site.
3. Contact Form 7, Manages multiple contact forms, plus you can customize the form and the mail contents flexibly with simple markup. The form supports Ajax-powered submitting, CAPTCHA, Akismet spam filtering and so on.
4. Contact Me, The quickest and easiest way to get a fully customizable contact form.
5. Custom Field Template, Adds the default custom fields on the Write Post/Page.
6. Custom Post Template, The plugin makes it possible to have more than a template for different types of posts. Templates are defined similarly to page templates, and will replace single.php for the specified post.
7. Database Manager by Lester Chan, Perform database tasks right within WordPress with scheduled backups.
8. Domain Mirror, Domain Mirror is a plugin to allow one WordPress installation to be accessed form more than one domain.
9. Download Manager by Lester Chan, A simple download manager to your WordPress blog.
10. Exec-PHP, Enables execution of PHP code in posts, pages and text widgets.
11. Get Recent Comments, Shows excerpts of the latest comments and/or trackbacks in your sidebar.
12. Google XML Sitemaps, Generates a special XML sitemap which will help search engines like Google, Bing, Yahoo and Ask.com to better index your blog.
13. Identify External Links, Searches the text for links outside of the domain of the blog. To these, it adds class=”extlink” (and optionally, target=”_blank”).
14. Peter's Login Redirect, Defines a set of redirect rules for specific users, users with specific roles, users with specific capabilities, and a blanket rule for all other users.
15. PhoneFactor, Phone verification system upon logging in for WordPress.
16. Post Editor Buttons, This plugin allows you add your own buttons to the post editor’s toolbar.
17. Post Expirator, Allows you to add an expiration date (minute) to posts which you can configure to either delete the post or change it to a draft.
18. Post Plugin Library, The shared code library for Similar posts, Recent Posts, Random Posts, Popular Posts and Recent Comments.
19. Pretty Link, Redirects any links from within WordPress.
20. Random Posts, Displays a list of randomly chosen posts. The output can be customised in many ways.
21. SEO Ultimate, Gives you control over title tags, noindex, meta tags, slugs, canonical, autolinks, 404 errors, rich snippets, and more.
22. Simple Crumbs, Generates a breadcrumb trail for pages and blog entries and pages.
23. User Access Manager, Manages the access to your posts, pages and files.
24. WordPress Importer, Import posts, pages, comments, custom fields, categories, tags and more from a WordPress export file.
25. WP Click Tracker, Adds automated link tracking to your posts and pages
26. WP Super Cache, Generates static html files from your dynamic WordPress blog.
27. WP-Ban, Bans users by IP, IP Range, host name, user agent and referer url from visiting your WordPress’s blog.
28. WP-DB-Backup, Allows you easily to backup your core WordPress database
29. WP-PageNavi, A well designed navigational system for WordPress posts.
30. WP-PostRatings, Gives users the ability to rate your posts.
31. WP-PostViews, Keeps track of how many times individual posts or pages have been viewed.

Users Interactivity Plugins

1. Business Directory, The Business Directory plugin for WordPress is an easy way to host a free directory page.
2. Contact Me, The quickest and easiest way to get a fully customizable contact form.
3. DISQUS Comment System, Is a service and tool for web comments and discussions.
4. Facebook Comments for WordPress, Allows your visitors to comment on posts using their Facebook profile. Supports custom styles, notifications, combined comment counts, recent comments
5. Get Recent Comments, Shows excerpts of the latest comments and/or trackbacks in your sidebar.
6. Gravity Forms, hands down the best contact form plugin for WordPress.
7. IntenseDebate Comments, Enhances and encourages conversation on your blog or website.
8. OptinPOP, Easily create unblockable, dynamic and fully configurable popups that can display any web page you choose within a lightbox popup window.
9. Page Peel, Banner ad in web corner.
10. PollDaddy Polls & Ratings, Allows you to create and manage polls and ratings from within your WordPress dashboard.
11. Share This, allows users to share your content through email and 50+ social networks including Facebook and Twitter.
12. The Sliding Panels, Provides 5 types of JavaScript-powered Sliding Panels – Top, Bottom, Left, and Right side panels and a Modal Window floating above the main webpage.
13. Top Commentators Widget, Shows the top commentators in side bar.
14. Twitter Tools, Creates a complete integration between your WordPress blog and your Twitter account.
15. Wibiya, Boosts blogs / websites with rich and interactive features. (check out the footer at the bottom of this page)
16. WP UI – Tabs, Accordions, Sliders
17. WP-Polls, Adds an AJAX poll system to your WordPress blog. You can also easily add a poll into your WordPress’s blog post/page.

Site Design

1. Content Slider by SlideDeck, Allows you to easily create a content slider widget or slideshow on your WordPress blog without having to write any code.
2. Page Peel, Banner ad in web corner.
3. Syntax Highlighter MT, Self-contained code syntax highlighter developed in JavaScript
4. Theme My Login, Themes the WordPress login pages according to your theme.
5. TypeKit, The easiest way to use Real Fonts on your website .
6. WP UI – Tabs, Accordions, Sliders
7. WP-Typography, Improve your web typography with: hyphenation, space control, intelligent character replacement, and CSS hooks.

eCommerce Plugins

1. WP e-Commerce, Elegant easy to use fully featured shopping cart application suitable for selling your products, services, and or fees online.

Plugins for Developers

1. Gravity Forms, hands down the best contact form plugin for WordPress.
2. TypeKit, The easiest way to use Real Fonts on your website .