Hi Paul,
This is a bit tricky since I am an expert on specifically Dojo and not any other toolkit
I do hav quite good knowledge of a couple of others, like ExtJs and jQuery, but I wouldn't presume to be able to give a comprehensive rundown of the available widgets for each.
To see some of the available widgets and features of Dojo, check out the feature explorer for Dojo that provide a lotof the
unit tests for dojo, dijit and dojox, here;
http://dojocampus.org/explorer/#Dojo http://dojocampus.org/explorer/#Dijit http://dojocampus.org/explorer/#Dojox Cheers,
PS
http://unclescript.blogspot.com/