Pixpie - Optimize your images and speed up your site on WordPress
Website Grader - Grade your website's strengths and weaknesses in seconds.
Website Image Speed Test - Beautiful & easy free analysis of the images on your page
PageSpeed Ninja - One-click page speed boost for WordPress
OptimizeWP - WordPress speed optimization and maintenance service
WebSite Auditor - The techie's SEO spider: find site issues other tools miss