ChrisHilditch

Speed up page load by loading in a widgets area with AJAX.
This plugin creates a new ‘Ajax Widget Area’. The widget loads the widgets placed in the ‘Ajax Widget Area’ with AJAX, after the page has loaded.

Ajax Widget Area

This plugin creates a new 'Ajax Widget Area'. The widget loads the widgets placed in the Area with AJAX, after the page load.

GTmetrix

GTmetrix has created GTmetrix for WordPress – a WordPress plugin that actively keeps track of your WP install and sends you alerts if your site falls below certain criteria.
Run analyses, schedule reports on a daily, weekly or monthly basis, and receive alerts about the status of your site all from within your WordPress Admin!

GTmetrix for WordPress

Plugin isn't showing the toolbar link in the latest version of WP now :(

Fantastic plugin but...

GTmetrix can help you develop a faster, more efficient, and all-around improved website experience for your users. Your users will love you for it.

Ajax Widget Area vs GTmetrix for WordPress