Active Extra Fields allows you to validate custom fields and post taxonomies.
WordPress Post Tabs is a plugin for WordPress that will help you add as many tabs to your WordPress post or Page. So, say if you want to write some review, you can create various sections of the review post and display them in a tab view, i.e. separate tab for each section.
World Flags allows you to add country flags anywhere in your WordPress blog using simple shortcodes and/or widgets, or show visitor country flag and info based on their IP address.
WP Word Count is a plugin for WordPress that gives you word count statistics for your blog’s posts and pages. In addition to overall stats, WP Word Count also gives figures and details for the largest posts and pages of your blog as well as breakdowns for each of your blog’s authors.
yPHPlista integrates PHPlist, the famous open-source, free and powerful mailing list software, with WordPress smoothly.
Google Analytics for WordPress is the most complete Google Analytics plugin for WordPress. Of course, you could just copy the tracking code into your theme and be done with it, but then you’d miss a whole lot of features that this plugin has to offer you.
SEO Ultimate gives you control over title tags, noindex/nofollow, meta tags, rich snippets, slugs, canonical tags, autolinks, 404 errors, rich snippets, and much more.
SI CAPTCHA Anti-Spam adds CAPTCHA anti-spam methods to WordPress on the comment form, registration form, login, or all.
WP SlimStat is a simple but powerful real-time web analytics plugin for WordPress. It doesn’t require any subscription to external statistic services: all metrics are kept on your local server, private and accessible to your eyes only.
WP-Stats-Dashboard displays your blog’s stats graph plus your blog traffic, social engagement and social influence directly in your dashboard. See how you’re ranking on Alexa, check out your Technorati authority, monitor your ranking across multiple sites and much more.