AJAX asynchronous calls without update panel

Is the UpdatePanel always needed to make Asynchronously calls to the server? I was catching up with the client side capabilities for the framework using the $get and $sys client classes and seem to provide a lot of functionality. Any samples, tutorials where I can go to get some reference. I went through the AJAX framwework documentation but no help.

No, you can also use webservices or pagemethods take a look at these links:

http://www.asp.net/ajax/documentation/live/overview/AsynchronousLayerOverview.aspx

http://www.asp.net/ajax/documentation/live/tutorials/ExposingWebServicesToAJAXTutorial.aspx

http://www.asp.net/ajax/documentation/live/tutorials/ConsumingWebServicesWithAJAXTutorial.aspx

Hope this helps,
Elias.