This guide covers everything from tutorials and best practices to working with JavaScript and the Drupal API. You can also view a searchable API reference at http://api.drupal.org.
You are strongly encouraged to contribute code back to the community. For more information, see the Contribute code section of the Getting Involved guide. There you will find detailed information on submitting patches and maintaining your own project.
For information on upgrading and backwards compatibility, see On backward compatibility: the drop is always moving.
Comments
Stand-alone download of tutorials, etc.
Probably worth adding that you can download the tutorials by clicking on the "Printer-friendly version" link on the page you want. This not only creates a print-friendly version of that page, but all the pages below in the hierarchy.
So the Drupal 7 module developers' tutorial can be downloaded in its entirety here:
http://drupal.org/book/export/html/1074360
Or all of this jive at once (apparently) from here:
http://drupal.org/book/export/html/316
good tip
I'm sure this will be a help for many