Optimal Title – This plugin allows you to optimize the title of your blog post in order to improve your search engine rankings.

Ultimate Tag Warrior- The best tag system for WordPress.

Google Sitemap Generator – This plugin will enable you to automatically generate a Google sitemap for your blog.

Show Top Commentators – This plugin encourages feedback and discussion by rewarding the top commentators with a link back to their site in the sidebar.

Related Posts – This plugin will find other blog posts that are related to the current post. This encourages extra page views and keeps readers at your blog for a longer period of time.

Super Archive – One of the best archives system.

WP-Cache – This plugin is an extremely efficient caching system that will make your site much faster.

WP-ContactForm – This plugin allows your readers to easily email you. It also helps avoid spam.

Popularity Contest – This plugin determines which of your posts are most popular and then puts them in the sidebar.

Adsense Deluxe – This plugin makes it easy to implement Adsense into your blog.

Sociable – This plugin helps you spread your content through social bookmarking sites like Digg, del.icio.us,reddit, and others.

Feedburner Feed Replacement – This plugin directs all of your feed traffic to Feedburner, ensuring accurate readership stats. This plugin will also convert any existing subscribers from the old feed to the FeedBurner
one.