While the ArcGIS JavaScript API is built on top of Dojo, you can use JavaScript libraries like JQuery or ExtJS in your applications. At version 2.0 we released a compact build of the ArcGIS JavaScript API. The compact build is small (~30kb) and does not include the dijit namespace on initial download so its a great option for those who wish to use a framework other than Dojo. The SDK contains a sample that shows how to work with the ArcGIS JavaScript API and JQuery or ExtJS..