Creating custom blocks in Drupal 7 seems like a pretty straightforward process in Drupal 7. You first implement hook_block_info() to tell Drupal about your block, then you implement hook_block_view() to set the contents of the block for the user. The API pages on these functions explain how to do this, and developers who spend a small bit of time working with these functions can probably get their block working.
When working with Drupal 7's Form API, I often need to call a JavaScript function after the #AJAX event has fired. This was quite difficult in Drupal 6, but Drupal 7 offers a nice mechanism to do so. In this tutorial, we will be going over a basic example on how to create a JavaScript function that is fired after an #AJAX function has completed. To do so, we will be looking at Drupal's Ajax Commands, and how we can use the system provided callbacks, as well as define our own custom callbacks, to enhance our Drupal forms.