WYSIWYG

http://drupal.org/project/wysiwyg_imageupload
http://drupal.org/project/imce_wysiwyg

These two modules add buttons to the editors through WYSIWYG API.
And they work quite fine, especially the first one.

WYSIWYG has a button plugin which serves as an example:

Basically, the plugin is just these 2 small files:
break.inc

<?php
function wysiwyg_break_plugin() {
  $plugins['break'] = array(
    'title' => t('Teaser break'),
    'vendor url' => 'http://drupal.org/project/wysiwyg',
    'icon file' => 'break.gif',
    'icon title' => t('Separate the teaser and body of this content'),
    'settings' => array(),
  );
  return $plugins;
}
?>

break.js

(function ($) {
// @todo Array syntax required; 'break' is a predefined token in JavaScript.
Drupal.wysiwyg.plugins['break'] = {

  /**
   * Return whether the passed node belongs to this plugin.
   */
  isNode: function(node) {
    return ($(node).is('img.wysiwyg-break'));
  },

  /**
   * Execute the button.
   */
  invoke: function(data, settings, instanceId) {
    if (data.format == 'html') {
      // Prevent duplicating a teaser break.
      if ($(data.node).is('img.wysiwyg-break')) {
        return;
      }
      var content = this._getPlaceholder(settings);
    }
    else {
      // Prevent duplicating a teaser break.
      // @todo data.content is the selection only; needs access to complete content.
      if (data.content.match(/<!--break-->/)) {
        return;
      }
      var content = '<!--break-->';
    }
    if (typeof content != 'undefined') {
      Drupal.wysiwyg.instances[instanceId].insert(content);
    }
  },

  /**
   * Replace all <!--break--> tags with images.
   */
  attach: function(content, settings, instanceId) {
    content = content.replace(/<!--break-->/g, this._getPlaceholder(settings));
    return content;
  },

  /**
   * Replace images with <!--break--> tags in content upon detaching editor.
   */
  detach: function(content, settings, instanceId) {
    var $content = $('<div>' + content + '</div>'); // No .outerHTML() in jQuery :(
    // #404532: document.createComment() required or IE will strip the comment.
    // #474908: IE 8 breaks when using jQuery methods to replace the elements.
    // @todo Add a generic implementation for all Drupal plugins for this.
    $.each($('img.wysiwyg-break', $content), function (i, elem) {
      elem.parentNode.insertBefore(document.createComment('break'), elem);
      elem.parentNode.removeChild(elem);
    });
    return $content.html();
  },

  /**
   * Helper function to return a HTML placeholder.
   */
  _getPlaceholder: function (settings) {
    return '<img src="' + settings.path + '/images/spacer.gif" alt="&lt;--break-&gt;" title="&lt;--break--&gt;" class="wysiwyg-break drupal-content" />';
  }
};

})(jQuery);

Any ideas on what can be done?