Creating a menu from a categories table

[eluser]skunkbad[/eluser]
I've been having a go at making a menu of categories from my categories table, and have seen some examples online (that I didn't really like or didn't work), and was wondering if anyone has a great way to do it.

Code:

CREATE TABLE `product_categories` (
  `category_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `category_name` varchar(24) NOT NULL,
  `parent_id` int(10) unsigned NOT NULL,
  PRIMARY KEY (`category_id`),
  UNIQUE KEY (`category_name`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8;

I'd like to be able to make the menu with nested unordered lists, based on the category relationships as parent/child. One of my goals is to allow the categories to have unlimited depth, and I've spent quite a bit of time trying to work something up, just to scrap it.

If anyone has some sample code, a link to a good tutorial, or would like to contribute (because this is going in my Community Cart application), I'd be very thankful.