I just finished up my session on async calls at TechEd and wanted to share the demos with the attendees and anyone else who cares to take a look.
In the talk I demoed working with the Dispatcher to get work put onto the UI thread at the appropriate time, but spent most of the talk working through a simple UI workflow example with a synchronous method, a Begin/End async method, an Async/Completed version, a Task Parallel Library (TPL) version, and a Async CTP (Task-based Async Pattern) approach. I finished off with some coverage of Reactive Extensions (Rx), showing an example of an auto-complete textbox that looks up customer data through async service calls.
The demo code includes both a Silverlight and a WPF version of the app, but since TPL and the Async CTP stuff is not available in Silverlight yet but will be in a future version, the WPF code is the more complete.
You can download the full sample code here: AsyncDemo.zip.