If you are a web developer and haven't seen Ext framework you should take a look.  The widgets offered can allow you to create rich internet applications which will eventually eliminate the need for client applications.  The libraries make fetching  an XML document and immediately presenting the data to the user without refreshing the page trivial (AJAX).  In this respect, it is a very similar framework compared to jQuery. 

Lately, I've been working with Ext JS in order to create a new statistics program for vBulletin called ionStats. Ext JS provides "a cross-browser JavaScript library for building rich internet applications".  To create an application simply download the library, code a few lines of JavaScript  and you have a rich WEB 2.0 interface.  Take a look here to see how I created an XML Grouping Grid using Ext JS.  Simple and quick. 

John and I have been debating which is better, Ext JS or Ext GWT.  He recently wrote a blog about Ext GWT here: Google Web Toolkit.  In my opinion Ext GWT is inferior because you need to create your application using Java and then convert it into JavaScript - take a look at the output here. I prefer to work directly with the JavaScript library rather than going through multiple tiers of coding/encoding and converting.  I see the potential for more bugs and errors to appear using this method, as John has recently pointed out a bug here:

1. Click here: http://extjs.com/examples/tabs/advanced.html
2. Close tab #7 and then look to the left of the tab control
3. You should see a large blank area - the bug! This was created using GWT.
   

Now do the same thing with the advanced tab created by Ext JS - http://extjs.com/deploy/dev/examples/tabs/tabs-adv.html

Amazingly the same bug on the same control doesn't appear when using Ext JS to build your applications proving my point further.  I'll defer to someone else creating a blog on why they think Ext GWT is superior.  Perhaps this will spur John into blogging mode. :)