Developing Applications Using Reverse Ajax
Reverse Ajax allows updates to be pushed from the server to the browser or browsers so that all users are aware of changes made. DWR's reverse Ajax introduces a very neat way to manage this transfer of information. It takes responsibility for deciding which techniques (polling, comet or piggyback) are best to use in each situation. This article compares three reverse ajax techniques (polling, comet, piggyback) supported by DWR. This reverse ajax article demonstrate how easily a chat web page can be created using reverse Ajax to an existing web application. The web page is a simple multi-user chat demo, allowing a number of users to see the messages that each submits. Reverse Ajax is used to collect the messages, and server-side browser manipulation updates the pages with the results
http://today.java.net/pub/a/today/2007/03/22/developing-applications-using-reverse-ajax.html

DWR official site and dwr documentation
This is DWR official site. The dwr documentation contains basic getting started guide, dwr configuration, dwr examples tutorials, and links to various direct web remoting (DWR) resources available on the web.
http://getahead.org/dwr/documentation

AJAX made simple with DWR
This tutorial gets you started using AJAX with DWR in your own projects.
http://www.javaworld.com/javaworld/jw-06-2005/jw-0620-dwr.html

Ajax file upload progressbar using DWR
In this article, author has described how to develop an Ajax-based file upload progress bar using portlet and DWR. This article uses Apache Commons FileUpload for uploading files to server. FileUploadProgressListener is used to measure the upload process. Client side java script code retrives file upload process from FileUploadProgressListener using DWR and updates the progressbar.
http://www.ibm.com/developerworks/web/library/wa-aj-dwr/?ca=dgr-lnxw06AjaxDWR