I Recommend This allows your visitors to simply recommend or like your posts instead of commenting.
WP Breaking News Mail allows you to send an email to your subscribers each time a post is published in one or more categories.
Akismet filters out your comment and track-back spam for you, so you can focus on more important things.
Jetpack supercharges your self-hosted WordPress site with the awesome cloud power of WordPress.com.
Share Buttons by Lockerz / AddToAny helps people share, bookmark, and email your posts & pages using any service, such as Facebook, Twitter, Google, StumbleUpon, Digg and many more.
Sharexy is a powerful social sharing, bookmarking, and blog monetization tool.
Super RSS is a jQuery based RSS reader widget, which displays the RSS feeds in the widget in an attractive way.
Twitter Avatar Reloaded adds a new field to the comment form to get the user’s Twitter usrename and uses it to replace the Gravatar with their Twitter avatar when the comment is displayed.