The code bellow is to be used in any module. It requires cck module to be installed. The advantage of this code is that it allows you to use labels and field definitions done through the cck ui. It allowed me to build a custom form based in the fields previously defined, it saves time and keeps your custom form consistent with the content type form.

I was trying to do the same on drupal 6.x I used to do with drupal 5.x to post a form inside a node. In oder words, to embed a node add form inside the body text area of a page. But I was getting fatal errors. I went to drupal.org site and found out that 6.x doesn't include some files when rendering the pages.

http://drupal.org/node/312189

Basically this is what I used to do on Drupal 5.x: