Example for easy dependency loading in user-scripts, compatible with Firefox (Greasemonkey) and Chrome (native; haven't tried Tampermonkey). Because Chrome doesn't allow `@require`, this technique is useful if you're too lazy to sync up a homebrew Chrome extension with an equivalent Greasemonkey script.

template.user.js

// ==UserScript==
// @name         <name>
// @match        <URL patterns for activation>
// @description  <description>
// ==/UserScript==

/**
 * Outermost IIFE for bootstrapper.
 * @param main Function encapsulating the real work of the script [required]
 * @param dep_urls Array of URLs to dependencies [default: empty array]
 * @param dep_refs Array of references to dependencies from window scope [default: empty array]
 */
(function bootstrap(main, dep_urls, dep_refs) {
    dep_urls = dep_urls || [];
    dep_refs = dep_refs || [];
    // Inner IIFE for recursive dependency loading.
    // This is an extension of Erik Vold's technique.
    (function load() {
        var script = document.createElement('script');
        if (dep_urls.length > 0) {
            // Load dependencies until the list is exhausted...
            script.src = dep_urls.shift();
            script.addEventListener('load', load);
        } else {
            // ... then inject the main script (as text) using arguments from the window scope.
            script.textContent = '(' + main.toString() + ')(' + dep_refs.join(',') + ');';
        }
        document.body.appendChild(script);
    })();
})(
    __main__,
    ['//rawgit.com/mbostock/queue/master/queue.min.js'],
    ['jQuery', 'queue']
    // In this example, I assume that jQuery is already present on the page,
    // so my user-script can piggyback off the existing jQuery reference.
);

// This is where the actual functionality of the user-script is specified.
// Arguments correspond to the dependency references given above.
function __main__($, queue) {
    // TODO
}

Very neat metaprogramming hack. I understand what this achieves, but I'll have to ask you what the alternatives are when you have time.

Thanks for documenting the IIFE: I'd been confused by this convention for some time, but unable to Google it without a name.