Last month I wrote a Firefox 3.0 extension which launched yesterday – https://addons.update.mozilla.org/en-US/firefox/addon/8267

From the official Wikia blog:

One of our core values at Wikia Search is Community. We want everyone to be able to participate in the Wikia Search project. That’s why we are proud to introduce Wikia Evolution, our new Firefox toolbar. You can download it here, or via Mozilla’s Firefox Add-On Library.

The mission of Wikia Evolution: To empower users to interact with search.

We want to make it dead-simple for you to add URLs into our index under appropriate keywords. Already, we’re the cutting edge when it comes to incorporating user feedback into our search results, so much so that Google is experimenting with eerily similar features. Wikia Evolution pushes the envelope even further. It allows you to quickly and easily add the web page you are on into Wikia Search, directly from your browser, for whatever keyword is appropriate. Instant indexing! Then, you can modify the search result to make it really killer, all without leaving the page you’re on.

The release was even covered by Techcrunch!

http://www.techcrunch.com/2008/08/06/wikia-evolution-to-help-suck-search-data-from-google-yahoo/

Like everything at Wikia, the toolbar is open source. A public SVN is up at http://people.swlabs.org/~bartek/websvn/listing.php?repname=SearchUI&path=%2Fcool%2Ftoolbar%2F and you can download the code from the Mozilla add-ons site.