New book: Pragmatic Ajax
I like the cross platform idea, it's not just Java or .Net, but this book covers more.

- Building Rich Internet Applications with Ajax. What is Ajax. Why now? Wither now?
- Ajax In Action. What it means to Ajaxify a web application.
- Ajax Explained. Client-side JavaScript. DOM manipulation. Server access.
- Google Maps Made Easy. Folks are awed by Google Maps, but it isn't rocket science (apart from the satellite pictures). See how to implement your own Google Maps-like application using DHTML.(partial extract...)
- Ajax Frameworks. Why you need a framework. Introduction to Dojo and Prototype. (partial extract...)
- Ajax UI, Part I. Using Ajax and JavaScript to provide a rich client user interface.
- Ajax UI, Part II. Standard patterns. Web forms and effects. A look at the things that you shouldn't do when deploying Ajax applications. (partial extract...)
- Degradable Ajax. Degrading gracefully with old browsers, and browsers with JavaScript disabled.
- Debugging Ajax. Tools, techniques, and tricks.
- Server-side frameworks. Java, .NET, PHP, and Rails
- Beyond Ajax. Mozilla XUL, Microsoft HTA, Flash as an Ajax component.
- Ajax Futures. E4X, Canvas, SVG, JSON.