Here's Widget library from Wiredesignz
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/**
 * Widget Plugin 
 * 
 * Install this file as application/plugins/widget_pi.php
 * 
 * @version:     0.21
 * $copyright     Copyright (c) Wiredesignz 2009-09-07
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
class Widget
{
    public $module_path;
    function run($file) {        
        $args = func_get_args();
        $module = '';
        /* is module in filename? */
        if (($pos = strrpos($file, '/')) !== FALSE) {
            $module = substr($file, 0, $pos);
            $file = substr($file, $pos + 1);
        }
        list($path, $file) = Modules::find($file, $module, 'widgets/');
        if ($path === FALSE) {
            $path = APPPATH.'widgets/';
        }
        Modules::load_file($file, $path);
        $file = ucfirst($file);
        $widget = new $file();
        $widget->module_path = $path;
        return call_user_func_array(array($widget, 'run'), array_slice($args, 1));    
    }
    function render($view, $data = array()) {
        extract($data);
        include $this->module_path.'views/'.$view.EXT;
    }
    function load($object) {
        $this->$object = load_class(ucfirst($object));
    }
    function __get($var) {
        global $CI;
        return $CI->$var;
    }
} 
Example
// application/widgets/Hello_world.php
class Hello_world extends Widget
{
    function run() {
        $this->render('hello_world');
    }
} 
In your view call the static “run” method on the widget class:
widget::run('hello_world');