According to some stats, this is the most popular plugin for Wordpress. It helps visitors/readers know what the most popular pages or posts are on a blog. The most popular posts are listed on the side of the page.
This is another very popular plugin that adds a Digg button after every blog post. Readers who like your posts can vote for it by “Digging” it. However, there have been some security flaws reported with this plugin and an alternate plugin called “Digg That” has been developed.
The Akismet plugin usually comes installed as a default when you install Wordpress for the first time. It checks the comments on your blog and compares them to its database to determine if they are spam. It requires a Wordpress API key which you can get by signing up for an account at Wordpress.com.
The Stats plugin provided you with statistics about traffic to your site. You can customize the settings according to your needs to get data about visitors to your site. Also requires an API key.
A very popular plugin that helps you integrate Adsense code onto your blog. Again, you can customize the settings of the ads for example, how many Ads or Adlinks you want per page, where you want them on the page and what the size should be.
You can use this plugin to link to another post on your blog. Makes your work easier by giving you the option to enter the post ID of your other posts instead of the complete hyperlink.
FriendsRoll lets your readers show you that they appreciate your content and let's them have their link displayed on your blog. A very good plugin to demonstrate a community feel.
This plugin integrates with IM services like MSN, AIM, Yahoo chat and Google chat. Visitors to your site can see whether you are online. Comes in different flavors of icons and widgets.
This is just a list of plugins that I think are very useful and should be a part of every blog. You can suggest your own favorites in the comments below.
