Reverse all of the text in the posts on your home page on April 1st. It does not affect titles, meta information, or HTML tags.
Twitter User is a simple plugin which adds an additional field to the authors profile in which they can add their twitter username.
Easy AdSenser manages all aspects of Google AdSense for a blog: insert ads into posts and sidebar, and add a Google Search box. Easy and complete! It is available in Spanish, Portuguese and French.
These two plugins are designed to help web designers easily demo there WordPress themes. For example, you want to demonstrate 10 themes over the same content, this plugin will allow you to do same without having to install multiple databases/instances of WordPress.
Control the number of posts per page, pages per page, and comments per page that appear in the admin listings of posts, pages, and comments.
Front-end Editor is a plugin that lets you edit posts or pages directly from your site. No need to load the admin backend just to correct a typo.
Display widgets only on certain pages.
The WordPress MindReader Plugin is similar to speech-to-text applications but instead of actually speaking, MindReader reads what’s on your mind (web cam required) and outputs your thoughts as text in the WordPress editor.
[removed, April Fool's Joke]
Restrict the usernames that new users may use when registering for your site.
Improve the inbuilt WordPress search by automatically making WordPress search for posts by relevance. Custom templates allow you to fit the plugin into the look and feel of your blog.
Helps readers share, save, bookmark, and email your posts and pages using any service, such as Delicious, Digg, Facebook, Twitter, and over 100 more social bookmarking and sharing sites. The button comes with Add to Any’s customizable Smart Menu, which places the services visitors use at the top of the menu, based on each visitor’s browsing history.
Control the number of posts that appear on the front page, search results, and author, category, tag, and date archives, independent of each other, including specific archives.
The plugin allows you to set up an automated e-mail that gets sent out to first time commenters on your blog, enticing them to come back or subscribe to your RSS.
Configure SMTP mailing in WordPress, including support for sending e-mail via SSL/TLS (such as GMail).