Easily add a sidebar widget displaying live stats about your WordPress blog including your website’s number of posts, authors and comments.
Corey Salzano‘s plugin Sidebar Stats Widget plugin queries your website’s MySQL database and counts the total number of authors who have posted at least one blog post, counts total number of published articles and approved comments then displays them in your sidebar. You can customize appearance and title of the widget. Install and activate then add it to your site from Dashboard -> Appearance -> Widgets page.