Taxonomy is a great tool in Drupal for categorizing information, unfortunately it is not often very "pretty" for the end user to interact with. Taxonomy Term Tree Widget addresses this deficiency by generating a pleasant, familiar tree structure from the target vocabulary's terms and their corresponding hierarchies. There is one problem, however, and that is that it is very difficult to filter the visible terms programmatically. The list can be filtered using a view (a setting accessible in the widget configuration form) however such a simplistic approach may not be flexible enough for most applications.
