Do you visit a particular site or blog that doesn't have tags, labels or categories and you would have liked to see which post is read by most people?
Try using Tag Cloud Generator.
This is a simple and free website where you just type in the url address of the site or blog you want to see tags and once you click on the 'generate' button, it will create for you the popular posts that people are reading on that website.
Better still, for administrators, webmasters and owners, you can use Tag Cloud Generator in your site. Just type in your site's URL address, let the engine generate tags for you then hit the "Get HTML source" button and paste it on your site as you would any other html code.