One of my favorite sample applications, and one that we are using for this month's launch events around Windows Vista and Office 2007, has just been released to the web so you can download it and try it out. It's DinnerNow and it's a comprehensive solution that highlights many technologies and best practices of the .NET Framework 3.0 (and some AJAX, IIS7 and Powershell thrown in to boot).
The fictional DinnerNow company provides a service by aggregating the menus from partner restaurants and allowing customers to order meals for delivery online. It then splits and dispatches those orders to the restaurants for fulfillment, allows the restaurants to receive and process the orders, and finally notifies delivery drivers to pick up and drop off the meals.
Take a look at the cool user experiences presented via the ecommerce ASP.NET 2.0 website (featuring ASP.NET AJAX and Windows CardSpace), the Sidebar gadget for tracking orders, and the kiosk app built with WPF. There's even a cool mobile app for delivery drivers.
Check out the slick usage of WCF where it's hosting services on HTTP and MSMQ transports. Oh, and the workflows for ordering processing modeled and executed with Workflow Foundation are pretty interesting too.
Now, all the functionality of the .NET Framework 3.0 illustrated by DinnerNow is awesome by itself. But throw in the management capabilities like being able to see the health of the WCF service hosts, and even track the individual workflow instances, and you've got one killer reference architecture application.