There are hundreds of WordPress plugins available. Most of them are great, but you cannot use them all as they would slow down your blog . I’ll list 15 plugins that I personally find very useful and that I advice you to use on your WordPress blog.

1. HeadSpace 2 SEO

HeadSpace 2 is a great all-in-one SEO plugin. It will help you manage your meta-data: you will be able to create custom titles, descriptions and tag your posts.

2. Google XML Sitemap

Google indexes articles much quicker if you have a sitemap. This plugin will automatically create an XML the sitemap for you and will notify Google, Yahoo, Bing and Ask about the updates on your blog.

3. WP Super Cache

This plugin  will speed up your blog significantly and make your pages load way faster. If you have many visitors on your website this plugin is definitely for you as it will prevent your server from crashing.

4. WordPress Related Posts

This plugin will display contextually related posts. If a visitor likes one of your articles then one of the best things that you can do to make him/her stay more on your blog is to display a few articles on the same topic.

5. WordPress Comment Remix

With the help of this plugin you can add a reply link to each comment. This will help you encourage the conversation and get more comments.

6. WP-DB Manager

Using this plugin you never lose your content. The plugin can email the entire WP database to you every day.

7. Akismet

Akismet is a great tool to fight against spam. It is very useful especially if you receive lots of spam comments.

8. Sociable

This plugin will automatically add social bookmarking buttons to your posts, pages and RSS feed.

9. WordPress Popular Posts

This plugin will display your most popular posts. It is very useful as it will make your readers visit more pages and spend more time on your website.

10. WP-Gravatar

This plugin lets you use Gravatar, OpenAvatar, Wavatar, Identicon, monsterID or Favico.ico files with your comments.

11. Upcoming Posts

Upcoming Posts will notify your readers when you will post a new article. This plugin is helpful to maintain your visitors’ interest.

12. WP Greet Box

This plugin detects the referrer URL (where your visitors are coming from) and automatically displays the corresponding greeting. You can also set a default greeting message suggesting your new visitors to subscribe to your RSS feed.

13. Vidoop Connect

Vidoop Connect make it easier to sign up to your blog by allowing your visitors to use their existing Yahoo, Google, Facebook and MySpace accounts.

14. Top Commentators

This plugin is useful to increase the number of comments on your blog. It will automatically display the persons with the biggest number of comments.

15. WP125

This plugin helps you manage 125×125 banner ads on your blog. It adds a new “Ads” menu to the WordPress admin and offers you plenty of options for displaying the ads.