Few months ago I started to take a look at new rich clients technologies such as Java web start, lazlo, xul, xaml etc...
But it seems like there is also another trend, launch with google new products, based on manipulating datas in old fashion html pages like google suggest, gmail using Ajax.
For examples you can take a look a cocoon ajaxified forms or even at mappy (that seems to use some kind of ajax too).
Today julien, pointed this impressive example of interactive DOM manipulation.
Interesting times :)