A service I just found out about: Silktide SiteScore. It checks your blog/site in several ways, including HTML correctness, popularity, how many people link to it, whether it includes several features, its accessibility, its speed, etc..
Then it gives you a nice score. I’ve just scored 8.3! According to them, “Your website is ranked #1,295 out of 42,352 SiteScores!” Enough to add a button to the right sidebar, I believe. 
One thing about it, though: taking the test several times (it’s free) may give different results (I got 8.1 and 8.3 without changing anything), just due to normal Internet speed variations. And the popularity rankings will, of course, change (hopefully, improve) with time. I wonder whether the button will change by itself without me taking the test again… Oh well, we’ll soon see.
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The checks for Accessabilty are not perfect - mind you there are many ways of interpreting the requirements - which means to get a good score you may well end up building your site to a set of standards that is a biased one. Having saiod that though it may not be a bad thing. Well done for getting in the top 1300. What was your score breakdown?