WebsiteGrader.com is an easy to use, free, quick health checkup for the SEO rank of your website. Their algorithm identifies the low-hanging fruits than you can easily pluck, to take your site ranking up a few notches.
But just like many things in life, this one too should be used in the right context. Use WebsiteGrader as a beginning, but not the end of your webstore optimization process. There are many things that a real human SEO consultant can offer that a tool like this cannot.
“Computers are incredibly fast, accurate and stupid; humans are incredibly slow, inaccurate and brilliant; together they are powerful beyond imagination.” — Albert Einstein (or whoever said it)