The wordpress plugins are arranged broadly by category of usage. As far as I know, all these plugins are compatible with the latest WordPress version. Please feel free to suggest great plugins in comments that I can add to this list.
Manage WordPress Comments

• Subscribe To Comments - Allows readers to recieve notifications of new comments that are posted to an entry.
• WP AJAX Edit Comments - Allows users and admins to edit comments on a post inline using AJAX.
• Get Recent Comments - displays excerpts of the most recent comments and/or trackbacks that have been posted to the articles in your blog.
• Close Old Posts - Closes comments on old posts without any DB queries.
• WP Grins - allows you to put clickable smilies on your post and comments forms.
• WordPress Paged Comments - allows comment paging. Useful for those very popular blog entries receiving many comments.
• Live Comment Preview - the simplest way to get live comment previews on your site.
• Show Top Commentators - Encourage more discussion from your readers, by displaying their names and number of comments they have made recently to your sidebar.
• WordPress Gravatar Plugin - outputs the gravatar based on the commenters email address.
• MyAvatars - shows MyBlogLog’s avatars in your comments
• Comment Relish - Sends a thank you e-mail to your first time commentators.
• Favatars - displays the favicon associated with the commenter’s website.
• Brian’s Threaded Comments - adds a ‘Reply to this comment’ link to every comment. Makes it easy for people to reply to comments and discuss better.
• Dofollow - lets you remove the nofollow attribute from your comments.
• OpenID Comments for Wordpress - allows users to leave comments using their OpenID.
• Extended Comment Options - allows you to switch comments and/or pings on or off for batches of existing posts.

Stop WordPress Spam

• Akismet - intelligently blocks spam comments. Checks your comments against the Akismet web service to see if they are spam or not.
• Spam Karma 2 (SK2) - is an anti-spam plugin for the WordPress meant to stop all forms of automated Blog spam effortlessly, while remaining as unobtrusive as possible to regular commenters.
• Bad Behavior - is a set of PHP scripts which prevents spambots from accessing your site by analyzing their actual HTTP requests and comparing them to profiles from known spambots.
• Math comment spam protection - Adds a math question to comments form to detect human input and block automated spambots.
• WP-Contact Form with Spam Protection - creates a contact form on your blog, through which your readers can contact you easily.

Expert WordPress SEO

• Google XML Sitemaps Generator - creates a sitemap of all articles on your WordPress blog. Helps Google and other search engines index every article you write.
• Permalink Redirect - replies a 301 permanent redirect, if requested URI is different from entry’s (or archive’s) permalink. It is used to ensure that there is only one URL associated with each blog entry.
• All in One SEO Pack - Optimizes your Wordpress blog for Search Engines (Search Engine Optimization).
• Head META Description - Insert HTML META description tags using post excerpts.
• SEO Title Tag - Optimize your wordpress title tags for search engines. Mass edit the title tags of posts, pages, category pages, tag pages etc.
• Enforce www. Preference - will help preserve your permalinks by enforcing your no-www or yes-www preference and will strip off index.php from the ends of URIs.
• Optimal Title - allows you to have your blog name tacked on to the end of the page title instead of having it appear first.
• Quick META Keywords - will automatically add META Keywords tags to every single post based on categories under which the article is categorized.

Easy WordPress Navigation

• Related Posts - Returns a list of the related entries based on active/passive keyword matches. Increase pageviews by providing targeted related content.
• WP-PageNavi - Adds a more advanced page navigation to Wordpress, which is very useful for navigation on index and category pages.
• Evermore - Abbreviate all posts when viewed on multiple post pages. Helpful to create expandable posts summaries in Wordpress. Combine with Less that changes the (more…) link so it displays the entire post, not just the part after the “more”.
• Random Redirect - Allows you to create a link to a random post on your blog. Lets readers browse in a StumbleUpon-like fashion.
• Lightbox JS Plugin - used to overlay images on the current page into neat Javascript-powered overlay popups.
• WordPress Mobile Edition - shows an interface designed for a mobile device when visitors come to your site on a mobile device.
• Popularity Contest - keeps a count of your post, category and archive views, comments, trackbacks, etc. and uses them to determine which of your posts are most popular.
• Extended Live Archive - implements a dynamic, AJAXified way of digging into the archives of a blog.
• Landing Sites - When visitors is referred to your site from a search engine, it shows them related posts to their search on your blog.
• Clean Archives - designed to display your archive listings in a clean and uniform fashion. It lists the Month / Year, the day of the month the article was published, the title of the article, and the number of comments that have been made on each article.
• Custom Query String - set the number of posts (custom queries) for every single page on your website like categories, archives, or search results pages.
• Feed List - very useful for adding other RSS feeds to your site.
• Sidebar Widgets because it allows you to move things (widgets) around, in and out of your sidebar. Not required for WordPress 2.2 and above.
• KB Advanced RSS Widget - a wordpress widget that gives you complete control over how RSS feeds are parsed for your sidebar.
• Category Cloud Widget - Adds a sidebar widget to display the categories as a tag cloud.
• Adhesive - lets you make the posts “sticky”, such that the posts will remain at the top of the page.

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