Free WordPress Plugins
Jetpack by WordPress.com
To get started with Jetpack, download and install the plugin. Once you’ve installed Jetpack you’ll get access to all the delightful features below.
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.
Best free SEO Plugins all time
Improve your WordPress SEO: Write better content and have a fully optimized WordPress site using the WordPress SEO plugin by Yoast.
Google XML Sitemaps
This plugin will generate a special XML sitemap which will help search engines to better index your blog.