Othman Ouahbi has a very nice example on his blog on creating automatic updating select-boxes with Ajax.
If you change the first select-box, it updates the next selectbox accordingly.

Ahsanul Bari created a nice list of links to articles on the use of Ajax in CakePHP. Some of the parts covered are:

• Getting Started
• AutoComplete
• Ajax Redirect
• Ajax Validation
• Encoding
• Ajax Uploader

Previously (in CakePHP 1.1) it was best to add an exit or return after you redirect method like:

$this->redirect('controller/action');
exit();

In CakePHP 1.1 if you need to display an image or piece of HTML with a link to an action, you need to instruct cake NOT to escape the contents of the "Title" attribute with the last false statement like this: