Eliminate Render Blocking CSS

eliminate-render-blocking-css.com provides an API for extracting the
critical path css from your site. This plugin inlines the results for every page
in your header section and deferres the loading of the rest of the styles.

You have to create a free account,
to be be able to use this plugin. Generation of critical path css is always free
for your front-page.

Some Features:

• Eliminate render-blocking CSS on your front-page. Use a premium account to
  include critical CSS for all your pages and both desktop and mobile
  devices.
• Unobstrusive generating and loading of the critcal css, falling back to your
  common CSS, when the service shouldn’t be available
• Automated deferred CSS loading, when you are using the standard WordPress
  style loaders (wp_register_style and wp_enqueue_style)
• Following Googles recommendations on loading critical CSS to 100%
• Critical CSS caching, both in your sites transients and on
  eliminate-render-blocking-css.com
• Background cache refreshing. One time cached, your site always gets a cached
  version, silently refreshed, when the caching interval ends