This plugin allows you to easily insert a wide variety of links into your wordpress documents with the following tag style:
[ln wikipedia]topic[/ln]
[ln php]htmlentities[/ln]
[ln amazon]978-0321396853[text]Eclipse Web Tools Platform[/text][/ln]
Or you can add links by clicking the ‘ln’ button inside of the wysiwyg editor. This will bring up a dialog box where you enter in the necessary data for that particular link
New link types can be easily added and existing links can be easily modified from the wordpress options page.
The following types of links are currently supported by default (with more on the way):
<ul>
<li>amazon</li>
<li>gravatar</li>
<li>php</li>
<li>twitter-rss</li>
<li>wikipedia</li>
<li>wppost</li>
</ul>

linkle

Easily embed links to wikipedia topics, amazon book sales, php documentation, and more with [ln linktype]topic[/ln].

asimeon

Thomas Riechert

The Wikipedia Widget shows a Wikipedia search-formular and its search results for the current post or page on your sidebar. On other sites (like category or front-page) it can defined any default search-keywords or other input-field.
The search results were Ajax-based fetched from the <a href="http://en.wikipedia.org/w/api.php" rel="nofollow ugc">Wikipedia-API</a>.
Main Features: 
<ul>
<li>Define a default search string or get the current post title</li>
<li>Show or hide the search form or define an alternative search form within the page</li>
<li>Use cache for the search results for better speed </li>
<li>Results are clear formatted, with links and pictures</li>
</ul>
Be free for testing and suggest improvements.
<h3>Tickets</h3>
<ul>
<li>Check given Wikipedia-URL at backend</li>
<li>plugin page at a-simeon.de</li>
<li>improve faq</li>
</ul>

Wikipedia Widget

Shows a simple Ajax based Wikipedia search-formular and the results for the current post/page title or default keywords.

linkle vs Wikipedia Widget