WooCommerce is the most popular WordPress eCommerce plugin. And it’s available for free. Packed full of features, perfectly integrated into your self-hosted WP site.
WordPress SEO by Yoast
Improve your WordPress SEO: Write better content and have a fully optimized WordPress site using Yoast’s WordPress SEO plugin.
W3 Total Cache
Easy WP Performance Optimization (WPO) using caching: browser, page, object, database, minify and content delivery network support.
Jetpack by WordPress.com
Jetpack adds powerful features previously only available to WordPress.com users including customization, traffic, mobile, content, and performance tools.
Easy Digital Downloads
Sell digital downloads through WordPress with this complete digital downloads management plugin. Comes with a lot of addons.
Simple but effective plugin that allows you to extensively clean up your WordPress database and optimize it without doing manual queries.