This plugin automatically add links to published posts to your Facebook wall or pages, in addition, it integrates the comments both your blog, and back to facebook.  You can have a high comment count without people actually visiting your site, which is good for SEO.

By Marcel Bokhorst | Visit plugin site

Used by millions, Akismet is quite possibly the best way in the world to protect your blog from comment and trackback spam. It keeps your site protected from spam even while you sleep.

The plugin shows excerpts instead of contents in your blog, single posts and pages excluded. It tries to display your custom excerpt text and if it doesn’t find it it will show an automatically generated excerpt. You can also define an excerpt length (default is 500) and a custom read more link.

Automatically generate featured image for new/old posts if Post Thumbnail is not set manually. In addition to post attachment, it also support external image, Youtube, Vimeo, DailyMotion. This is really useful for updating your site if you haven’t used a featured image in the past.

Reward your readers by automatically placing a link to their last blog post at the end of their comment. Encourage a community and discover new posts.

This plugin shows the featured image on your post list in WordPress.  Easy to see if you need to change them without clicking inside the post.

This is a plugin originally authored by Steve Smith. It detects all ways to access your original WordPress feeds and redirects them to your FeedBurner feed. This one is enhanced and now it can redirects feeds for category and tag also.

This plugin makes it simple to add Google Analytics to your WordPress blog, adding lots of features, eg. custom variables and automatic clickout and download tracking.

Add Google Picasa albums to your blog posts, pages and sidebar.

This plugin will generate a special XML sitemap which will help search engines like Google, Yahoo, Bing and Ask.com to better index your blog.

Bring the power of the WordPress.com cloud to your self-hosted WordPress. Jetpack enables you to connect your blog to a WordPress.com account to use the powerful features normally only available to WordPress.com users.

Automatically copies all posts to a LiveJournal or other LiveJournal-based blog. Editing or deleting a post will be replicated as well.   You can direct where the comments go as well.

Turn your WordPress blog into a mobile website/blog.  (I LOVE THIS PLUGIN!)

Send a email to author automatically while someone reply his comment.

Multiply blog traffic by strengthening on page SEO, increasing the number of indexed pages, auto convert search terms into post tags, and more.

SEO Smart Links provides automatic SEO benefits for your site in addition to custom keyword lists, nofollow and much more.

A simple plugin to manage sharing and following. You can obviously see it in use on the site on the sidebar, as well as the bottom of the post.

This plugin automatically detects tags to place against posts using existing tags as well as a simple formula that detects common tag formats such as Acronyms, names and countries. Whereas other smart tag plugins only detect a single occurance of a tag within a post this plugin will search for the most used tags within the content so that only the most relevant tags get added.

Automatically send a ‘thank you’ e-mail to those who comment on your blog. This plugin engages the visitor by reminding them to check back for responses or new blog posts. The plugin is highly configurable with multiple messages, variable delay and restrictions.

Enables advanced features and plugins in TinyMCE, the visual editor in WordPress.

Wibiya toolbar settings plugin

Displays the WordPress.com stats graph, your traffic and social metrics monitoring on your dashboard.

Outputs your Blogroll links to a Page or Post. Add wp-blogroll to a Page or Post and all your WordPress links/Blogrolls will be rendered. This extremely simple plug-in enables you to create your own Links page without having to write a custom template.The output can easily be styled with CSS. Each category with its links is encapsulated in a DIV with a classname called “linkcat”. All the links are attributed with the class “brlink”.

This plugin allows you to add a social blogroll to your blog. The blogroll will display your bookmarks, their freshness and their latest post-title.

Posts a Twitter status update when you update your WordPress blog or post to your blogroll, using your chosen URL shortening service. Rich in features for customizing and promoting your Tweets.