Facebook menu Fixer is a script that put an icon in the top bar to fix the sidebar menu when you're scrolling. Use this script with greasemonkey or tampermonkey.

facebook_menu_fixer

// ==UserScript==
// @name        facebook menu
// @namespace   http://killua.me/
// @description Keep the menu aviable without scroll
// @include     http*facebook.com/
// @include     http*facebook.com/?sk=nf
// @include     http*facebook.com/lists/*
// @include     http*facebook.com/groups/*
// @version     1
// @require     https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js
// ==/UserScript==

/**
 * Menu fixer for facebook. Allow you to keep the menu when you need.
 */
(function ($) {
  $('#pageHead').prepend('<img id="killua-menu" style="border: 1px solid #222; cursor: pointer; float: left; margin: 0 4px; height: 21px; width: 21px; " src="http://dl.dropbox.com/u/9861549/menu-fb-icon.png" />');

  $myobject = $('#leftCol');
  $demenu = $('#killua-menu');

  $demenu.bind('click', function() {
    $myobject.css('position', 'fixed');
  });
})(jQuery);