Some of my first steps baby steps (in the goal to masterize Drupal). Might help others...please contribute especially if you're already pretty good at Drupal and know what we (newbies) will be looking to do...
Drupal API documentation
No PHP knowledge required.
Goal: I was looking to display the list of all books in a node (and more generally trying to understand the design and logic of Drupal).
I'm using the book.module has an example, but this might also apply to all other modules.
I came across this good article: http://drupal.org/node/26502
The following is what I learned and extrapolated, from that article (read it first) and by digging a little further:
$block = module_invoke('module_name', 'block', 'Operation', delta);
module_name: Is the module name.