This fork is meant to work with acts-as-taggable-on and creates new tags if they aren't found.
IT USES TAG NAMES just like the usual :tag_list text field in a hidden field, not IDs.
jQuery Tokeninput: A Tokenizing Autocomplete Text Entry
Tokeninput is a jQuery plugin which allows your users to select multiple items from a predefined list, using autocompletion as they type to find each item. You may have seen a similar type of text entry when filling in the recipients field sending messages on facebook.
Documentation, Features and Demos
Full details and documentation can be found on the project page here: