Twistermc
Social Bookmark plugin can display image links or text links. Even do it as a dropdown list and it blends with your sites CSS style very well.
Digg This
The popularity depends on the post being digg. Detects incoming links from Digg and provides a link back so people can Digg your post.
Submit your post to popular social bookmarking sites.
FlickRrss
This plugin for WordPress allows you to display Flickr photos on your weblog.
Pull your Flickr album & display on your blog.
Flickr Post Bar
Show your image collection within your editor for easy post writing
Facebook Fan Box Widget
Display facebook fan box as widget in your WordPress blog.
Facebook Like Button
The Like button enables users to make connections to your pages and share content back to their friends on Facebook with one click.
WP-FacebookConnect
WP-FacebookConnect adds Facebook functionality to Wordpress using the Facebook Connect APIs.
Plugin to embed Wordpress Blog into Facebook Platform.
Publish to Facebook
Publishes posts, pages or both to your Facebook Mini-Feed directly from Wordpress.
Tweet Blender
Blends any mentions of your username with user profile thumbails.
Twitter Tools
A complete integration between your WordPress blog and Twitter. Bring your tweets into your blog and pass your blog posts to Twitter.
Tweetable
Tweetable is intended to help integrate Twitter into your blog. It can automatically tweet links to your blog posts as they are published. It can display your lastest tweet in your sidebar and add a tweetmeme widget after your posts.
Adds a sidebar widget to display Twitter updates
Twitter Sharts
'Shart' your twitter status anywhere within your wordpress blog posts or pages!
Twitter LiveBlog
Twitter LiveBlog integrates with Twitter and lets you liveblog on your Wordpress blog.