From the vast number of plugins available for WordPress it can be difficult to know which ones to install first after you have setup your new WordPress installation. I've put together a list of the plugins that I use on this site in the hope that others find it useful.
If you have any other favorite plugins that are not listed here, please leave details in the comments and why you think they are brilliant (and also which category they fall into).
Akismet is quite possibly the best way in the world to protect your blog from comment and trackback spam. It keeps your site protected from spam even while you sleep.
A great plugin which creates a backup of your WordPress site (both the filesystem and MySQL database) and uploads it to a number of cloud services (FTP, Amazon S3, DropBox, Google Storage, etc) or can just send it by email. Multiple backup schedules can be set, as can the number of total backups to keep. Notifications of backups (or just failed backups) can be sent by email.
The most important thing you can do with your WordPress site is to keep it constantly up-to-date. Running the latest version of WordPress and your plugins will keep you protected against virtually all attacks. This plugin sends email notifications to the admin by email if a new version of WordPress, plugin or theme becomes available.
This plugin will generate a special XML sitemap which will help search engines like Google, Yahoo, Bing and Ask.com to better index your blog. Essential to ensure your site gets maximum exposure.
The Disqus comment system replaces your WordPress comment system with a much more advanced system hosted and powered by Disqus. The interface is very clean and enhances your user's experience with extra features. In addition, users can use Disqus without needing to register on your site - something that can put off a lot of people.
Insert Link Class allows you to customise the Styles drop-down menu in TinyMCE (the visual post editor in WordPress). You can specify the Text to display on the menu and the CSS class to be applied to the selecte text in the editor. Unfortunately styles aren't live in the editor, but you can see their effects when you preview your post.
Enables advanced features and plugins in TinyMCE, the visual editor in WordPress. It includes extra features such as font size and family selection, and support for creating and editing tables (essential!).
This plugin makes it simple to add Google Analytics to your WordPress blog, adding lots of features, eg. custom variables and automatic clickout and download tracking. If you want to get an insight into how your users access and navigate your site, then you'll need Google Analytics.
Manages downloads on your site, view and show hits, and output in posts.
Both of these plugins provide syntax highlighting for code snippets on your blog (either using SyntaxHighlighter or GeSHi). There is little to choose between them but I have found incompatibilities with Syntax Highlighter when using the PageLiens Platform theme .
Integrates FancyBox by Janis Skarnelis into WordPress - allows you to include thumbnails in your posts that will be enlarged is a pretty manner when your visitors click on them, and without navigating them away from the current page.
This plugin adds the ability to create a list of tags, similar to a category list.