• Automatic Links – Automatically adds HTML anchor tags to plain text links and email addresses embedded in the content of posts and pages.
• Category Icons – Assign icons to your categories to appear next to post titles on the index, single post, archive and search pages.
• WP-Polls – A great AJAX polling system to place polls as widgets or into posts. You can have multiple polls throughout your site.
• WP Authors – Want to have a list of authors on your sidebar alongside your categories? This plugin allows you to place a widget that lists and links to authors on your blog.
• WP No Category Base – Would you rather have “yoursite.com/categoryname” or “yoursite.com/category/categoryname” ? This plugin allows the former for a shorter URL.
• WordPress Popular Posts – Retrieves the most active entries of your blog and displays them with your own formatting (optional). Use it as a widget or place it in your templates.

Also check out my Ten Favorite WordPress Plugins and my post about using WordPress as a CMS.