Plugin #1: FeedBurner FeedSmith

This probably won’t directly affect your seo on site, but the better reach your blog posts have, the more chance someone has to read it, and link to it if they were inspired by what you say. So you have to write good content first, and then this plugin becomes 100% more effective at building links.

Plugin #2: Dagon Design Sitemap Generator

A must have for every website, XML sitemaps should be generated on the fly and updated whenever you add a new page or write a new post. This is not just another XML sitemap plugin, but rather a true sitemap generator which is highly customizable from its own options page in the WordPress admin panel. Some of its features include: support for multi-level categories and pages, category/page exclusion, multiple-page generation with navigation, permalink support, choose what to display, what order to list items in, show comment counts and/or post dates, and much more.

Plugin #3: Friend Connect Commenting Plugin

You can now allow visitors to log in with their FriendConnect ID, and leave a comment with that same ID. This means that your visitors can log in with their Google, Yahoo!, AIM or OpenID account, by just clicking a button

Plugin #4: Google Analytics

The interfaces are fancy, and the fine grained stats and AdSense integration make it a particularly powerful tool when you’re seeking to push a product online using AdSense.

Plugin #5: Platinum SEO Pack

If you are already using All In One SEO Pack, this plugin will automatically import all the settings, that you have defined using All in one SEO plugin. You just need to verify the options, through Setting->Platinum SEO page of your wordpress blog. Platinum SEO Pack is also compatible with earlier versions of wordpress, though I recommend you to upgrade to the latest version of wordpress.

Plugin #6: Search Excerpt

It extracts out the search keywords, scans the content of matched post entries, and displays document snippets around the keyword, with that specific keyword highlighted. It adds a filter in get_the_excerpt() function so no modification needs to be done to WordPress’ 1.5/2.x theme. For other themes, make sure during “the loop” in search.php, it calls the_excerpt() to display the post entries.

Plugin #7: SRG Clean Archives

This plugin is designed to display your archive listings in a clean and uniform fashion that’s search engine friendly on a dedicated page or in your sidebar.

Plugin Features: It lists the Month / Year, shows total post count for the month (enabled by default), the day of the month the article was published, the title of the article (permalink to article) and the number of comments (enabled by default) that have been made on each article.

Plugin #8: WordPress Database Backup

WordPress database backup creates backups of your core WordPress tables as well as other tables of your choice in the same database.