The document lists 11 essential WordPress plug-ins for enhancing blogs, categorized by functionality such as slideshows, content management, contests, mobile design, social sharing, related content, comments, speed optimization, SEO, analytics, and event management. It provides alternative suggestions for each plug-in and general tips for selecting quality plugins. Key criteria for choosing plugins include compatibility with the latest WordPress version, user popularity, recent updates, active support, and the potential value of premium options.