I am looking for a good solution for a probably typical problem of managing models with HABTM association in Rails.

Let's assume that we have two models -- products and categories:

Products
  has_many :categorizations
  has_many :categories, :through => :categorizations
Categories
  has_many :categorizations
  has_many :products, :through => :categorizations
Categorization
  belongs_to :product
  belongs_to :category

Pat Shaughnessy is developing modified auto_complete plugin which can allow to manage one-to-many (and many-to-many) association:

For someone that would be enough, but I don't really like so many text fields. I guess it is possible to combine the Ryan Bates' screencasts used by Pat in a slightly different way, namely, using one text field with autocomplete:

Also it would be better to remove from the list of suggested tasks (one-to-many), or products|categories (many-to-many) those which have been already added.

In the case of products-categories relationship, such auto completion would be used both in the form for product, and in the form for category.

I hope that there is an existing plugin for that. I am not very experienced in Ruby, and don't really know how to implement such logic by myself.

Any help is appreciated!