Quick and Dirty Bookmarklet for the excellent https://github.com/KrofDrakula/microdata-tool

microdata-tool-bookmarklet-pretty.js

// modified from code of "JQuerify" bookmarklet
// http://www.learningjquery.com/2009/04/better-stronger-safer-jquerify-bookmarklet
(function() {
    function z(a, b) {
        var c = document.createElement("script");
        c.src = a;
        var d = document.getElementsByTagName("head")[0], e = !1;
        c.onload = c.onreadystatechange = function() {
            !e && (!this.readyState || this.readyState === "loaded" || this.readyState === "complete") && (e = !0, b(), c.onload = c.onreadystatechange = null, d.removeChild(c));
        };
        d.appendChild(c);
    }
    function d() {
        a.innerHTML = msg, b.appendChild(a), window.setTimeout(function() {
            typeof jQuery == "undefined" ? b.removeChild(a) : (jQuery(a).fadeOut("slow", function() {
                jQuery(this).remove();
            }), otherlib && ($jq = jQuery.noConflict()));
        }, 2500);
    }
    var a = document.createElement("div"), b = document.getElementsByTagName("body")[0];
    otherlib = !1, msg = "", a.style.position = "fixed", a.style.height = "32px", a.style.width = "220px", a.style.marginLeft = "-110px", a.style.top = "0", a.style.left = "50%", a.style.padding = "5px 10px", a.style.zIndex = 1001, a.style.fontSize = "12px", a.style.color = "#222", a.style.backgroundColor = "#f99";

    //load jquery (if not already loaded)
    if (typeof jQuery != "undefined") {
      msg = "This page already using jQuery v" + jQuery.fn.jquery + "... proceeding", d();
    } else {

      typeof $ == "function" && (otherlib = !0), z("http://code.jquery.com/jquery-latest.min.js", function() {
          return typeof jQuery == "undefined" ? msg = "Sorry, but jQuery wasn't able to load" : (msg = "This page is now jQuerified with v" + jQuery.fn.jquery, otherlib && (msg += " and noConflict(). Use $jq(), not $().")), d();
      });
    }

    //load jquery.microdata.js
    typeof $ == "function" && (otherlib = !0), z("https://github.com/KrofDrakula/microdata-tool/raw/master/jquery.microdata.js", function() {
        return typeof $.microdata == "undefined" ? msg = "Sorry, but jquery.microdata.js wasn't able to load" : (msg = "jquery.microdata.js loaded " );
    });

    //load schema.js
    typeof $ == "function" && (otherlib = !0), z("https://github.com/KrofDrakula/microdata-tool/raw/master/schemas.js", function() {
        // didn't find what to test schema.js against
        return typeof $.microdata == "undefined" ? msg = "Sorry, but schema.js wasn't able to load" : (msg = "schema.js loaded " );
    });

})();

microdata-tool-bookmarklet.js

javascript: (function(){function a(a,b){var c=document.createElement("script");c.src=a;var d=document.getElementsByTagName("head")[0],e=!1;c.onload=c.onreadystatechange=function(){!e&&(!this.readyState||this.readyState==="loaded"||this.readyState==="complete")&&(e=!0,b(),c.onload=c.onreadystatechange=null,d.removeChild(c))},d.appendChild(c)}function b(){c.innerHTML=msg,d.appendChild(c),window.setTimeout(function(){typeof jQuery=="undefined"?d.removeChild(c):(jQuery(c).fadeOut("slow",function(){jQuery(this).remove()}),otherlib&&($jq=jQuery.noConflict()))},2500)}var c=document.createElement("div"),d=document.getElementsByTagName("body")[0];otherlib=!1,msg="",c.style.position="fixed",c.style.height="32px",c.style.width="220px",c.style.marginLeft="-110px",c.style.top="0",c.style.left="50%",c.style.padding="5px 10px",c.style.zIndex=1001,c.style.fontSize="12px",c.style.color="#222",c.style.backgroundColor="#f99",typeof jQuery!="undefined"?(msg="This page already using jQuery v"+jQuery.fn.jquery+"... proceeding",b()):(typeof $=="function"&&(otherlib=!0),a("http://code.jquery.com/jquery-latest.min.js",function(){return typeof jQuery=="undefined"?msg="Sorry, but jQuery wasn't able to load":(msg="This page is now jQuerified with v"+jQuery.fn.jquery,otherlib&&(msg+=" and noConflict(). Use $jq(), not $().")),b()})),typeof $=="function"&&(otherlib=!0),a("https://github.com/KrofDrakula/microdata-tool/raw/master/jquery.microdata.js",function(){return typeof $.microdata=="undefined"?msg="Sorry, but jquery.microdata.js wasn't able to load":msg="jquery.microdata.js loaded "}),typeof $=="function"&&(otherlib=!0),a("https://github.com/KrofDrakula/microdata-tool/raw/master/schemas.js",function(){return typeof $.microdata=="undefined"?msg="Sorry, but schema.js wasn't able to load":msg="schema.js loaded "})})();

jsfiddle so that you can drag it directly to your bookmarks:
http://jsfiddle.net/peterhost/ZJfpL/14/embedded/result/

Hi! on some sites there is only alert about JQuery is loaded, but no microdata widget, and on another sites even no JQuery loaded alert - just nothing...:( on some https sites after clicking onto bookmarklet i get an alert, FF blocked unsecure content. Have you ever seen such misbehavior?

I try this code but this is not working

This currently does not work on Firefox due to incorrect MIME types (text/plain) of the URLs served by github.com/KrofDrakula/microdata-tool/raw/...:

La ressource à l’adresse « https://raw.githubusercontent.com/KrofDrakula/microdata-tool/master/jquery.microdata.js » a été bloquée en raison d’un type MIME (« text/plain ») incorrect (X-Content-Type-Options: nosniff).
Échec du chargement pour l’élément <script> dont la source est « https://github.com/KrofDrakula/microdata-tool/raw/master/jquery.microdata.js ». blog:1:1
La ressource à l’adresse « https://raw.githubusercontent.com/KrofDrakula/microdata-tool/master/schemas.js » a été bloquée en raison d’un type MIME (« text/plain ») incorrect (X-Content-Type-Options: nosniff).
Échec du chargement pour l’élément <script> dont la source est « https://github.com/KrofDrakula/microdata-tool/raw/master/schemas.js ».

(errors are in French)

Using those URLs instead fixed the issue:

• https://gitcdn.link/cdn/KrofDrakula/microdata-tool/5a2af7bc5b46389334a972b4ef49a7710773ec5c/jquery.microdata.js
• https://gitcdn.link/cdn/KrofDrakula/microdata-tool/5a2af7bc5b46389334a972b4ef49a7710773ec5c/schemas.js