PResponsive

This plugin will add a image below your posts, allowing your visitors to share your posts with their friends, on FaceBook, Pinterest, Google+, Twitter, Myspace, Friendfeed, Technorati, del.icio.us, Digg, Google, StumbleUpon, and other. After plugin is activated a buttons will appear after the content of the post.Clicking this button will bring the user to the bookmarking site. If the user isn’t logged in they will be prompted to do so. 
Post your articles to the social bookmarking sites and get traffic.

WP Social Bookmarking

WP Social Bookmarking plugin syndicates your blog posts in social networking sites.

bradvin

This plugin allows you to easily bookmark/favorite posts, pages and custom post types. When you ‘star’ a post a shortcut link will appear in the admin menu. 
Use this plugin if you constantly find yourself editing the same posts or pages, and are sick of showing the list of posts first, then finding the post, then clicking edit.
Steps to use
<ol>
<li>Go to Pages</li>
<li>Click the Star icon on a page.</li>
<li>Your page is now bookmarked!</li>
<li>Repeat for other pages you always edit.</li>
<li>Save time!</li>
</ol>
Plugin Features
<ul>
<li>Intuitive interface to bookmark posts using a star icon.</li>
<li>Zero settings! Activate and enjoy.</li>
<li>Works with posts, pages and any custom post types.</li>
<li>Dashboard widget listing all bookmarks.</li>
<li>Setting a bookmark is done in realtime with no page reload.</li>
<li>Bookmarks are added to the admin menu for quick access under a “Bookmarks” menu item.</li>
<li>Adds a Bookmarks view/filter to the listing pages.</li>
<li>Bookmark shortcuts are also grouped by post type within the WordPress admin bar.</li>
<li>Optional “Bookmark Title” quick edit field to customize menu labels</li>
</ul>
Filters
<ul>
<li><code>admin_bookmarks_post_types</code> – Filter to scope bookmarks to specific post types</li>
<li><code>admin_bookmarks_untitled_label</code> – Filter to customize the untitled label</li>
<li><code>admin_bookmark_feature-dashboard_widget</code> – Filter to disable the dashboard widget</li>
<li><code>admin_bookmark_feature-quick-edit</code> – Filter to disable the quick edit feature</li>
<li><code>admin_bookmark_feature-view</code> – Filter to disable the view feature</li>
<li><code>admin_bookmark_feature-admin-bar</code> – Filter to disable the admin bar feature</li>
</ul>
To disable a feature, add a small bit of custom code to your theme’s <code>functions.php</code> file:
<pre><code>add_filter( 'admin_bookmark_feature-dashboard_widget', '__return_false' );
</code></pre>

Admin Bookmarks

Bookmark your favorite posts, pages or custom post types within the WordPress admin

WP Social Bookmarking vs Admin Bookmarks