During my work developing Drupal sites I am quite often asked if I can provide a example of form elements for designers. This is so that they can test their designs with all possible form elements that might appear in a Drupal install and make sure that the theme we create will be robust and future proof. I often find myself forgetting how to create, say, a multi select element and needed a sort of cheat sheet that I could look form elements up on.
To this end I sat down and created a list of all of the Drupal form elements and packaged them into a module so that when the path 'form_elements' is loaded a very large form with lots of elements will be rendered. There is even a tabledrag form component in there, which is used quite a bit within the Drupal administration pages.