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.

Piotr Pesta

Wikipedia Anniversaries is a widget that lets your visitors to see important history dates from Wikipedia. Supported languages so far: Deutsch, Polish, English and Persian. More languages in the future. To customize style just edit style-wiki-this-day.css file. Cache support – 5 hours refresh rate.
If you would like to show your support for this software, please consider donating: <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=EEDF5TV3M2WVG&lc=US" rel="nofollow ugc">Donate via PayPal</a>.

Wikipedia Anniversaries

Wikipedia Anniversaries is a widget that lets your visitors to see important history dates from Wikipedia.

Wp-Wikipedia-Excerpt vs Wikipedia Anniversaries