The Author Image plugin for WordPress adds widgets that let you easily add author images on your site.
The Auto Thickbox plugin for WordPress automatically enables thickbox on thumbnail images (i.e. opens the images in a fancy pop-up).
The Bookmark Me WordPress plugin lets you display subscribe links to social sites such as Facebook, Google+, Twitter, and Pinterest.
The External Links plugin automatically marks outgoing links as such.
The XML Sitemaps WordPress plugin automatically generates a XML Sitemap files for your site and notifies search engines when they're updated.
The Ad Manager plugin for WordPress allows you to manage advertisement space on your site. (Premium)
The Contact Form plugin for WordPress lets you easily insert a contact form on your site. (Premium)
The Fuzzy Widgets plugin for WordPress lets you generate a fuzzy number of recent posts, pages, links, and comments. (Premium)
The Google Analytics plugin for WordPress lets you add Google Analytics support to your site. (Premium)
The inline widgets plugin for WordPress lets you embed any widget into the content of a post or page. (Premium)
The Nav Menus plugin for WordPress creates configurable navigation widgets that behave similarly to Silo Pages widgets. (Premium)
The Random Widgets plugin for WordPress lets you display a random number of posts, pages and links. (Premium)
The Redirect Manager plugin for Wordpress enables easy redirect of obsolete posts and pages as well as cloaking of affiliate links. (Premium)
The Related Widgets plugin for WordPress builds on your tags to generate a list of related posts or pages. (Premium)
The Script Manager plugin for WordPress lets you easily insert scripts, as well as meta tags and arbitrary html, in the header and footer of your site. (Premium)
The Semiologic Cache plugin for WordPress greatly increases the front-end performance of your site. A necessity when your site gets featured on traffic-heavy sites such as Reddit or Digg. (Premium)
The Semiologic SEO plugin for WordPress comprises various search engine optimizations for use with WordPress themes. (Premium)
The Semiologic Fixes plugin for WordPress includes a variety of teaks and fixes for WordPress and third party plugins. (Premium)
The Silo Widgets plugin for WordPress creates widgets to assist you in creating silo structured web sites. (Premium)
The Smart Links plugin for WordPress lets you (pre-)enter links like [text->link], where link can be a keyword or a key phrase. When no relevant link is found, the text appears without a link. (Premium)
The Version Checker plugin for WordPress adds version checking for plugins that are not stored in the official WordPress repository. (Premium)
The Widget Contexts plugin for WordPress lets you control when WordPress widgets display on your site. (Premium)