1. Akismet – Every WordPress site’s best friend.  Akismet is the first line of defense between your blog and an endless stream of comments attempting to sell you Viagra. It stops what it detects to be spam comments , and holds them in a special moderation qeue separate from your other comments. You can then review and delete them at your convenience. As your blog gets more popular, the number of spam comments you receive will increase, and Akismet will save you a significant amount of time in terms of catching and deleting each spam comment as it’s left on your blog.
2. All in One SEO Pack -A popular plugin with SEO folks, its All in One SEO Pack lets you insert meta tags, helps you with duplicate content, optimizing titles and more.
3. Broken Link Checker for WordPress – As your blog gets more and more posts, it can be difficult to go back and look for what has broken with time.  This plugin will check images and links and notify you via the dashboard when it locates something.  Just the other day I installed this on a clients WordPress site and found 102 broken links!
4. Google Analyticator – Google Analytics is a popular way of tracking your site visitors.  This plugin allows you to enter your code, and it will take care of making sure it gets to the right place in all of your themes.  However, this is a plugin that I can do without because I can manually put analytics code in footer.php but if the client needs to edit the code they can do it on their own.
5. Google XML Sitemap – Helps you generate XML enabled sitemap to help with indexing by search engines like Google, MSN, Ask and more.
6. No Self Pings – A nice little plugin that keeps pingbacks from showing up in your comments section when you link back to your own blog entries.
7. WordPress.com Stats – A stats system that helps you reduce the load on your server by using the WordPress.com servers to keep track of your stats for you.
8. WP Super Cache – Caches your pages as static HTML files as opposed to PHP files, which can take longer to process and display on your site.
9. Share This – This plug-in allows readers to add your blog posts to social bookmarking sites through an icon that appears at the end of each of your blog posts. Readers click the icon to select the social bookmarking site they prefer in order to save and share your post.
10. WordPress Database Backup – What would happen if something happened to your blog and all of your content was lost? You can avoid that possible tragedy by installing a WordPress backup plug-in. This plug-in backs up the core information in your blog (the main tables). There are also more sophisticated WordPress backup plug-ins such as the WP-DBManager plug-in that will allow you to further customize your backups.

Highlights

• New drag-and-drop widgets admin interface and new widgets API
• Syntax highlighting and function lookup built into plugin and theme editors
• Browse the theme directory and install themes from the admin
• Allow the dashboard widgets to be arranged in up to four columns
• Allow configuring the number of items to show on management pages with an option in Screen Options
• Support timezones and automatic daylight savings time adjustment
• Support IIS 7.0 URL Rewrite Module
• Faster loading of admin pages via script compression and concatenation