These are live examples from the Drupal 6 Examples for Developers Project on drupal.org. Try them out! To try the Drupal 7 examples, go to d7.drupalexamples.info.
To experiment with the code yourself, download the module code and play.
If you find problems or have suggestions and contributions, please create an issue in the issue queue.
The code is also indexed by api.drupal.org.