along with these even complex applications like word processing, spreadsheet processing etc are made using ajax.
google has released a new developer toolkit google web toolkit a framewordk to create robust ajax applications like google maps and gmail easier for developers, gwt is a java software development framework.
more from gwt site
dynamic, reusable ui components
create a widget by compositing other widgets. lay out widgets automatically in panels. send your widget to other developers in a jar file.
really simple rpc
to communicate from your web application to your web server, you just need to define serializable java classes for your request and response. in production, gwt automatically serializes the request and deserializes the response from the server. gwt's rpc mechanism can even handle polymorphic class hierarchies, and you can throw exceptions across the wire.
browser history management
no, ajax applications don't need to break the browser's back button. gwt lets you make your site more usable by easily adding state to the browser's back button history.
your gwt applications automatically support ie, firefox, mozilla, safari, and opera with no browser detection or special-casing within your code in most cases.
interoperability and fine-grained control