Autocomplete Deluxe is a cool Drupal contrib module that basically pimps up your site’s autocomplete elements. As I am sure you are aware, it can get sometimes difficult managing many taxonomy terms and assigning them to nodes using the default autocomplete field. Enter Autocomplete Deluxe.

This module uses the jQuery UI autocomplete element to provide a much more enhanced experience when selecting the terms in a taxonomy term reference field, for example. It allows you to both add new terms as you type them in and to select existing one via a handy drop down list. And it also means that you don't need to have any additional jQuery plugins added to your site's library.

To get started with Autocomplete Deluxe, install it like usual. Then head down to the admin page for managing the fields of a particular content type (admin/structure/types/manage/article/fields for the Article content type for example) and change the widget of the taxonomy term reference field to Autocomplete Deluxe. Save and then when you add or edit a node of that type, you should see the awesome new difference.

Hope this helps.