secure_wikipedia.user.js

// ==UserScript==
// @name Secure Wikipedia
// @include http://*/*
// @include https://*/*
// @description Changes links to Wikipedia articles to point to secure version
// ==/UserScript==

(function(){
    var links = document.getElementsByTagName("a");
    for (var i = 0; i < links.length; i++) {
        var wiki_regexp = /http:\/\/(..)\.wikipedia\.org\/wiki\/(.+)/;
        if (wiki_regexp.test(links[i].href)) {
            var matches = wiki_regexp.exec(links[i].href);
            links[i].href = "https://secure.wikimedia.org/wikipedia/" + matches[1] + "/wiki/" + matches[2];
        }
    }
})()