Below are 8 completely free WordPress plugins which will benefit any installation, whether its a personal blog, or a professional corporate site.
Contact Form 7
Contact Form 7 can manage 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.
Google Analytics by Yoast
The Google Analytics by Yoast plugin for WordPress allows you to track your blog easily and always stays up to date with the newest features in Google Analytics.
Jetpack adds powerful features previously only available to WordPress.com users including customization, traffic, mobile, content, and performance tools.
Simple Share Buttons Adder
The Simple Share Buttons Adder does exactly what it says on the tin – adds share buttons to all of your posts and pages, simply.
W3 Total Cache
The only WordPress Performance Optimization (WPO) framework; designed to improve user experience and page speed.
WordPress Zero Spam
WordPress Zero Spam blocks registration spam and spam in comments automatically without any additional config or setup. Just install, activate, and enjoy a spam-free site.
WordPress SEO by Yoast
WordPress out of the box is already technically quite a good platform for SEO, this was true when Joost wrote his original WordPress SEO article in 2008 (and updated every few months) and it’s still true today, but that doesn’t mean you can’t improve it further! This plugin is written from the ground up by Joost de Valk and his team at Yoast to improve your site’s SEO on all needed aspects. While this WordPress SEO plugin goes the extra mile to take care of all the technical optimization, more on that below, it first and foremost helps you write better content. WordPress SEO forces you to choose a focus keyword when you’re writing your articles, and then makes sure you use that focus keyword everywhere.