GromBeestje

The OAuth plugin for WordPress allows you to provide authentication against any 
OAuth provider. This plugin is uses the OAuth library by Manuel Lemos. The 
plugin allows the admin to select any from the services supported 
out-of-the-box by the said library. Additionally it is possible to configure a 
service manually, which means any site supporting the OAuth protocol can 
be used.

BlaatLogin: OAuth

This plugin turns your WordPress website into an OAuth Consumer. It allowsallows your users to sign in with any OAuth provider.

wokamoto

This is a plugin creating a new tweet including a URL of new post on your wordpress.
You can use specific tweet phrases by post authors. 
And You can also tweet short URL of your domain if you introduce the plugin <a href="https://wordpress.org/extend/plugins/short-link-maker/" title="Short link maker" rel="ugc">Short link maker</a>.
PHP5 Required.
<h4>Localization</h4>
<ul>
<li>English (en) – <a href="http://www.odysseygate.com/" title="Odysseygate.com" rel="nofollow ugc">odyssey</a></li>
<li>Japanese (ja) – <a href="http://dogmap.jp/" title="wokamoto" rel="nofollow ugc">wokamoto</a> (plugin author)</li>
<li>Belorussian (be_BY) – <a href="http://pc.de/" title="PC.DE" rel="nofollow ugc">Patricia</a></li>
<li>Dutch (nl_NL) – <a href="http://wpwebshop.com/blog" title="WPWebshop Blog" rel="nofollow ugc">Rene</a></li>
<li>German (de_DE) – <a href="http://www.creditriskmanager.com/" title="Credit Risk Manager" rel="nofollow ugc">Rian Klijn</a></li>
</ul>
If you have translated into your language, please let me know.
<h3>Licence</h3>
Released under the <a href="http://www.gnu.org/copyleft/gpl.html" rel="nofollow ugc">GPL license</a>.

Simple Tweet

This is a plugin creating a new tweet including a URL of new post on your wordpress.

BlaatLogin: OAuth vs Simple Tweet