The basic idea here is that you can easily link to the wikipedia entry for a given topic by putting the [wikipedia]topic[/wikipedia] tag into your post. The tag is replaced by a link that executes the wikipedia search form for that topic.
The plan is to augment this with a mouseover popup containing an excerpt from the wikipedia page.

Wp-Wikipedia-Excerpt

This plugin replaces [wikipedia]topic[/wikipedia] with a wikipedia search link for that term.

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.

Wp-Wikipedia-Excerpt vs Wikipedia Widget