$(document).ready(function($) {
    $("#content .contextual").prepend("<a href=\"#\">New</a>");
});

$(document).ready(function($) {
    var newLink = $("<a href=\"#\">New</a>");
    $("#content .contextual").prepend(newLink);
    $(newLink).click(function() {
        var parent = $(this).parent();
        var form = $("<form></form>");
        form.append("<input type=\"text\">");
        $(form).submit(function(e) {
            e.preventDefault();
            var name = $($(form).children()[0]).val();
            var splitPath = window.location.pathname.split("/", 5);
            var wikiPath = "/" + splitPath[1] + "/" + splitPath[2] + "/"
                    + splitPath[3];
            var parentName = splitPath[4];
            var newPathname = "/" + name + "?parent=" + parentName;
            window.location.assign(wikiPath + newPathname);
            return false;
        });

        $(this).replaceWith(form);
        form.children("input").focus();
        return false;
    });
});

Add some fugly javascript to pre-fill parent wiki page.