Dojo Toolkit is a powerful javascript library that has been choosed the last year for the official integration with Zend Framework. Zend_Dojo is the component that provides out-of-the-box dojo and dijit experience, and it's really easy to setup a bunch of accordion menus or other layout dijits in a rapid pace.
However, Dojo is not simple: if you want a simple library that makes you call end() instead of using the } brace, go for jQuery; if you want something powerful that can load a million records in a grid, choose Dojo.
So, the focus is on finding the best documentation for Dojo, to teach to us, php-based people, some hi-tech javascript; here I list some links that can help.

• SitePen Blog, corporate blog of a company whose employees develop Dojo for living. A must read for who wants to master dijit usage.
• Official Dojo Book for 1.x version, examples and comments for Dojo up to 1.2 version. There you will find all the plugins you can put in the dijit Editor, for instance.
• Dojo Book, a wiki where the official book is migrated. This will be the new point of reference, the php.net/manual of Dojo.
• Zend_Dojo reference manual, for who uses Zend Framework and Dojo, like me.
• Dojo Goodness, ten articles written from the author of Dojo: The Definitive Guide from O'Reilly, that illustrate practical examples of using dijits and Dojo core, much like SitePen's articles.

Hope you will find these resources useful... Good luck with unleashing the power of Dojo!