There are some great books from Packt publishing about Drupal 6, the latest version of Drupal (as of Feb 2010)

Drupal 6 JavaScript and jQuery at http://www.packtpub.com/drupal-6-javascript-and-jquery/book/mid/310309unjcci.

This is one of those books that make programmers like me salivate.  How many times have you wanted to make your clients websites fly about and wow their visitors.  I did get to dig deeper into it and added some really cool features to some of my clients websites. Matt Butcher is really smart. Oh and jQuery is a lot more palatable than coding in straight Javascript. Good job Matt. Some nice juicy examples. 

Enjoy - I did. - Selwyn