From ADO.NET’s Blog:

“To aid brainstorming and to better understand typical developer scenarios, the ADO.NET team created an internal prototype of a designer to let developers model the ADO.NET vNext “Conceptual” layer.
The designer in this CTP is an early prototype and only supports designing the “Conceptual” layer. The designer can also generate an Entity Data Model with 1:1 mappings from an existing database that you can use right away in your application while also graphically visualizing the “Conceptual” layer”

Dowload ADO.NET vNext Entity Data Model Designer Prototype CTP

Download ADO.NET vNext CTP – August 2006