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].

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.

linkle vs Wp-Wikipedia-Excerpt