In one of my recent project, I happen to use JQuery, JQueryUI & JQueryUI Theme roller.
JQuery is an exciting UI framework, with great ease of usage, samples, documentation & user experience. JQueryUI provides you with great UI components such as accordian, tabs, date, progress bar, roller & more. JQueryUI Themeroller, makes it easy to design your css & theme for the component. In a way take away the burden of user experience from a java developer :).