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].

Alexander Rauscha

InfoLink adds a Button to the Editor, so you can easy link words from your post to wikipedia, imdb (supports English/German/Espanol/Fran?ais wiki and imdb) or any site searched by google. Just select a word or sentence and click on the button or chose a service from the menu. The Word will be automatically searched and infolink will select the most meaningful result. (with the option to edit them)

InfoLink

Quickly add Links to Wikipedia, IMDB Sites or search for site/blog or news with Google. And New with 1.3 also your bookmarked Links.

linkle vs InfoLink