Choosing the right plugins for your blog can have an impact on many aspects of your blog from SEO and Optimization, to monetization.  I have included what I think are some of the best WordPress plugins to help you operate a successful blog and a few that are helpful but not necessary.

Akismet - Akismet checks your comments against the Akismet web service to see if they look like spam or not and lets you review the spam it catches under your blog’s “Comments” admin screen.

Broken Link Checker-  This plugin monitors links in your posts, pages, comments, blogroll, and custom fields (optional). When a broken link is detected, you have the option to be notified via the dashboard or email.

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.

Google Analytics for WordPress – Track your WordPress site easily and with lots of metadata: views per author and category, automatic tracking of outbound clicks and pageviews.

Growmap Anti Spambot - This plugin will add a client side generated checkbox to your comment form asking users to confirm that they are not a spammer. It is a lot less trouble to click a box than it is to enter a captcha and because the box is genereated via client side javascript that bots cannot see, it should stop 99% of all automated spam bots.

Link Within - LinkWithin is a blog widget that appears under each post, linking to related stories from your blog archive.

Network Publisher - Automatically publish your blog posts to multiple Social Networks including Twitter, Facebook Profile, Facebook Pages, LinkedIn, Blogger, Delicious, Foursquare, Tumblr, and more.

Old Post Promoter - The Old Post Promoter (OPP) is a WordPress plugin by the Blog Traffic Exchange. The purpose of the plugin is to promote old posts by sending them back onto the front page and into the RSS feed. It does it randomly choosing an eligible post and updating the publication timestamp. The post then appears to be the latest post on your WordPress blog.

Post Expirator - Allows you to add an expiration date to posts which you can configure to either delete the post, change it to a draft, or update the post categories.  This is great for sponsored posts as you can set the post to change to draft status after a specified number of days.

Sociable – One of the more popular social bookmarking plugins.  Sociable gives you the option of placing the icons above, below, or to the side as a Skyscraper Bar.

Tweet Old Post - Tweet Old Posts randomly picks your older post based on the interval specified by you. The primary function of this plugin is to promote older blog posts by tweeting about them and getting more traffic.

WhyDoWork Adsense - WhyDoWork Adsense allows you to insert Adsense ads on your blog without modifying the template with a variety of useful options.  One useful option is to set Adsense to display only after the post ages a certain number of days to give readers a chance to enjoy a period of ad-free reading.

WordPress Editorial Calendar - The editorial calendar gives you an overview of your blog and when each post will be published. You can drag and drop to move posts, edit posts right in the calendar, and manage your entire blog.

WordPress SEO  - WordPress SEO is the most complete WordPress SEO plugin that exists today for WordPress.org users. It incorporates everything from a snippet preview and page analysis functionality that helps you optimize your pages content, images titles, meta descriptions and more to XML sitemaps, and loads of optimization options in between.

WP DB-Backup - WP DB-Backup allows you to automatically schedule a backup of your WordPress Database tables and have the backup emailed to you.

WP-Optimize- WP-Optimize is a WordPress 2.9++ database cleanup and optimization tool. It doesn’t require PhpMyAdmin to optimize your database tables. It allows you to remove post revisions, comments in the spam queue, un-approved comments within few clicks.

WP Smush.it - Reduces image file sizes and improves performance.  Once you have it installed there is nothing left to do.  Images are compressed automatically when uploaded to your site.

WP Super Cache - This plugin generates static html files from your dynamic WordPress blog. After a html file is generated your webserver will serve that file instead of processing the comparatively heavier and more expensive WordPress PHP scripts.  By serving a static page WP Super Cache can speed up your site’s page load time dramatically.