A new set of Atlas-enabled ASP.NET 2.0 controls was released this month.  Check it out.
In the "Atlas" Control Toolkit, you'll find the following controls and extenders (click the links to see them in action!):

CascadingDropDown: Easily link drop downs, complete with asynchronous population and no postbacks!
CollaspiblePanel:  This extender allows panels on your page to collapse and […]