Wikimedia Bugzilla is closed!

There are a large number of manually and semi-automatically generated Firefox
search plugins on mycroft.mozdev.org for Wikipedia and related Mediawiki sites.
 Mediawiki could generate one of these automatically for each wiki based on what
it knows about the site.

A basic Firefox search plugin for the English Wikipedia looks like this:

   <search
      version="7.1"
      name="Wikipedia (en)"
      description="The free encyclopedia"
      sourceTextEncoding="0"
      method="GET"
      action="http://en.wikipedia.org/wiki/Special:Search"
      queryCharset="UTF-8">
   <input name="search" user>
   <input name="fulltext" value="fulltext">
   <input name="sourceid" value="mozilla-search">
   </search>
   <browser
      update="http://en.wikipedia.org/w/wikipedia-en.src"
      updateIcon="http://en.wikipedia.org/w/wikipedia-en.png"
      updateCheckDays="3">

The name and description can be encoded in any Mac OS character encoding that
Mozilla knows of, with sourceTextEncoding set appropriately; for example, name="
ウィキペディア" description="フリー百科事典" sourceTextEncoding="1" encoded in
Shift-JIS.  See
http://philringnalda.com/blog/2005/01/proper_charset_encoding_in_mozilla_firefox_toolbar_search_sherlock_src_files.php,
including the comments.