Module development and code questions

I'm using taxonomy_dhtml on my site. When a user clicks on a menu item, the menu expands. But I've added some jQuery so that when a user double clicks on an icon, he is taken to the page of the menu item's link.

I may be helping out with a project I'm working on - it's to do with online course enrollment / registration for a college. Is there a similar module which I can use?

Why do I not see any difference by the authorship module. If I put an author it still has my username - and no where does it say who wrote it.

Helo,

I am trying to port my module to Drupal 5.x.
The problem is, I need this file:

http://api.drupal.org/api/HEAD/file/developer/examples/node_example.module

However this link:

http://api.drupal.org/api/HEAD/file/developer/examples/node_example.modu...

Does anybody know if there is a module which checks if user has previously logged in? I want to make some action when user logs in to the system for the first time (i.e. show welcome message or send an e-mail to admin indicating that user logged in). I know I have to check users table but how to catch login action performed by user?

How would I go about creating a new filter.
I am new to drupal module develpment, but not new to PHP.