Migrating the articles:
  1. Change database name my_joomla_db to your joomla database and my_wordpress_db to your Wordpress database
  2. Change http://demo.joellipman.com/wordpress/ to the full URL of your WordPress site.
  3. If post_type is to be post then append with ?p= otherwise use ?page_id=.
Articles: 
------ MIGRATING JOOMLA v1.5.# CONTENT TO WORDPRESS v3.2.# ------
-----------------------------------------------------------------

INSERT INTO my_wordpress_db.wp_posts
SELECT
	id 'ID',
	1 'post_author',
	created 'post_date',
	created 'post_date_gmt',
	CONCAT(introtext, ' ', `fulltext`) 'post_content',
	title 'post_title',
	'' post_excerpt,
	CASE state WHEN '1' THEN 'publish' ELSE 'draft' END 'post_status',
	'open' comment_status,
	'open' ping_status,
	'' post_password,
	alias 'post_name',
	'' to_ping,
	'' pinged,
	modified 'post_modified',
	modified 'post_modified_gmt',
	'' post_content_filtered,
	'0' post_parent,
	CONCAT('http://demo.joellipman.com/wordpress/', '?p=', id) AS guid,
	'0' menu_order,
	'post' AS 'post_type',
	'' post_mime_type,
	0 comment_count
FROM
	my_joomla_db.jos_content
ORDER BY
	id


Importing the joomla categories to Wordpress: (still to do: sections as parent categories?)

SET @CountCategoriesAlreadyEntered:=(SELECT MAX(term_id) FROM my_wordpress_db.wp_terms);

INSERT INTO my_wordpress_db.wp_terms
SELECT
	(a.id + @CountCategoriesAlreadyEntered) 'term_id',
	a.title 'name',
	a.alias 'slug',
	0 'term_group'
FROM
	my_joomla_db.jos_categories a
ORDER BY
	a.id;


INSERT INTO my_wordpress_db.wp_term_taxonomy
SELECT
	(a.id + @CountCategoriesAlreadyEntered) 'term_taxonomy_id',
	(a.id + @CountCategoriesAlreadyEntered) 'term_id',
	'category' AS 'taxonomy',
	a.description 'description',
	0 'parent',
	(SELECT COUNT(c.id) FROM my_joomla_db.jos_content c WHERE c.catid=a.id) 'count'
FROM
	my_joomla_db.jos_categories a
ORDER BY
	a.id;	


INSERT INTO my_wordpress_db.wp_term_relationships
SELECT
	b.id 'object_id',
	(b.catid + @CountCategoriesAlreadyEntered) 'term_taxonomy_id',
	0 'term_order'
FROM
	my_joomla_db.jos_content b
ORDER BY
	b.id;
Importing Joomla jComments to Wordpress Posts:

...still to come...