Now that the Entity Framework is outside the scope of Orcas, they have their own CTP. Be warned that this CTP only works with Visual Web Developer Codename "Orcas" Express Edition June 2007 CTP.

http://blogs.msdn.com/adonet/archive/2007/07/02/ado-net-entity-framework-june-2007-ctp-now-available.aspx