Akismet is a spam protection plug-in which is developed by the creators of Wordpress. It eliminates practically all spam that will ever be posted on your blog using its huge database of comparison software to determine whether a comment is spam or not. This plugin is a must for everyone and you simple will not be able to live without it.
If you want your blog to rank highly on Google, you need to use various SEO techniques. This plugin simplifies the whole process by automatically optimizing your posts for search engines, allowing you to enter your own keywords and description, and more. All you have to do is fill out an amazingly simple form
This plugin is an excellent way of letting your readers contact you. It takes mere minutes to set-up and provides you with a completely customizable contact form. There is no better alternative.
Feedsmith redirects all of your site feeds at yoursite.com/feed to your Feedburner feed so that you can track your subscribers. It provides a simple service but is invariably useful.
Sociable adds small, very attractive bookmarking options at the end of your posts. Currently it offers over 50 social networking sites that you can choose from.
This plugin is pretty self-explanatory: it creates a Google-compliant sitemap that helps search engine crawlers index your website. It helps with SEO and thus brings more traffic to your blog.
Popularity contest rates your posts based on their popularity (how many people have viewed them, commented on them, and more). You can use this data to display your most popular posts to new readers - very handy.
Ultimate Tag Warrior enables you to very easily and efficiently add tags to your Wordpress posts. These tags help both your readers find your content and Technorati index it.