Androfire

<p>TDisplays links from del.icio.us, Technorati, Reddit, Digg and TailRank that is relevant to the current category of your blog. Eg: Your visitor browses the ?humor? category of your blog; the links will come from ?http://del.icio.us/tags/humor? and so on. This means that you do not have to change any code for each specific category.</p>


WP-ExternalFeed

Displays links from del.icio.us, Technorati, Reddit, Digg and TailRank that is relevant to the current category of your blog

Matthias Pfefferle

IndieWeb

joshfraz

<p>This plugin implements the <a href="https://www.w3.org/TR/websub/" rel="nofollow ugc">WebSub</a> protocol (formerly known as PubSubHubbub) for WordPress. It enables real-time notifications when your blog is updated and provides a subscriber API for other plugins to consume WebSub-enabled feeds.</p>
<h3>Publisher Features</h3>
<p>When you publish or update a post, this plugin automatically notifies WebSub hubs, which then distribute the update to all subscribers in real-time.</p>
<ul>
<li>Sends realtime notifications when you update your blog</li>
<li>Supports multi-user installations (WordPress MU)</li>
<li>Supports multiple hubs</li>
<li>Supports all feed formats used by WordPress (Atom, RSS2, RDF)</li>
<li>Adds <code><link rel="hub"></code> and <code><link rel="self"></code> declarations to feeds and HTML</li>
</ul>
<h3>Subscriber Features</h3>
<p>The plugin provides a subscriber API that allows other plugins (like feed readers) to subscribe to WebSub-enabled feeds using WordPress hooks.</p>
<ul>
<li>REST API callback endpoint for subscription verification and content delivery</li>
<li>Hub discovery from topic URLs (HTTP Link headers and feed content)</li>
<li>HMAC signature verification (SHA1, SHA256, SHA384, SHA512)</li>
<li>Full lifecycle hooks for integration with other plugins</li>
</ul>
<h3>Supported Specifications</h3>
<ul>
<li><a href="https://www.w3.org/TR/websub/" rel="nofollow ugc">WebSub W3C Recommendation</a></li>
<li><a href="https://pubsubhubbub.github.io/PubSubHubbub/pubsubhubbub-core-0.4.html" rel="nofollow ugc">PubSubHubbub 0.4</a></li>
</ul>
<h3>Default Hubs</h3>
<p>By default this plugin will ping the following hubs:</p>
<ul>
<li><a href="https://pubsubhubbub.appspot.com" rel="nofollow ugc">Demo hub on Google App Engine</a></li>
<li><a href="https://pubsubhubbub.superfeedr.com" rel="nofollow ugc">SuperFeedr</a></li>
<li><a href="https://websubhub.com" rel="nofollow ugc">WebSubHub</a></li>
</ul>
<p>Please contact us if you operate a hub that you would like to be included as a default option.</p>


WebSub (FKA. PubSubHubbub)

Best Update Plugin

A WebSub plugin for WordPress that enables real-time publishing and subscription capabilities.

WP-ExternalFeed vs WebSub (FKA. PubSubHubbub)