Embed Facebook lets you embed various Facebook objects (album, event, group, note, photo, or video) in a post or page.
mySimpleAds WordPress Ad Manager allows you to easily place your mySimpleAds Ads inside your WordPress posts, pages, or even right in your templates.
Plugin Test Drive lets you test any plugin before actually using it.
Theme-Check allows you to run checks on the current theme before uploading to WordPress. This plugin uses the same API and is kept more or less in sync with the WordPress.org uploader tool.
Wickett Twitter Widget allows you to display tweets from one or more Twitter accounts as a WordPress widget. As seen on WordPress.com.
Akismet checks your comments against the Akismet web service to see if they look like spam or not.
Facebook Like for Tags allows you to automatically share into Facebook when posting new articles with the same tags or categories.
Github Ribbon can be used to add Github ribbons to your website.
SyntaxHighlighter Evolved allows you to easily post syntax-highlighted code to your site without having to escape the code or anything. As seen on WordPress.com.
Ultimate Post Type Manager is an easy to use custom post type manager with a great UI.
Ultimate Taxonomy Manager is an easy to use taxonomy manager with a great UI.