The name of the carousel control is RadCarousel which is part of the Telerik.Windows.Controls.Navigation.dll under the Binaries directory that you should have downloaded along with our WPF Controls demo. To see RadCarousel in Microsoft Expression Blend you will have to add a reference to the navigation library in your project's references. You should then be able to see it under the Custom Controls pane in the Asset Library.
Hope you will find the above info helpful!
the Telerik team
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