Yes, you can achieve a TaskBar like functionality if you are using a RadWindowManager that exposes all windows in the current page.
I have created a simple demo that demonstrates how to use the RadWindowManager and a listbox with a horizontal orientation that is display over all RadWindows. Moreover, you can create your own ItemTemplate that looks like a minimized RadWindow and thus achieve better look as I have rather layout out the foundation of your work.
Note that I use the latest binaries from our Q2 release that are already online. I have also attached a solution based on Silverlight 3 as the popup control in Silverlight 2 seems to have some problems with focus. If you are going to adopt Silverlight 3 I would recommend to you our second solution as it's a little bit more neat. It uses a popup control that is functioning properly.
If you have any other questions concerning our controls, feel free to contact us immediately.
the Telerik team