Dojo is an incredibly powerful toolkit that provides a wealth of web development utilities that you don’t want to miss out on. In addition to coming packed with rich, turn-key Web 2.0 widgets for you to snap into your applications, it also includes the standard JavaScript library you’ve always wanted, facilities for compressing your code when it comes time for production, AJAX utilities, a suite of object oriented programming (OOP) constructs that reduces the boilerplate you’d otherwise have to write and maintain your own custom widgets, and more.

Website: http://www.onlamp.com/pub/a/onlamp/2007/11/01/the-mojo-of-dojo.html