You can now download a version of the ADO.NET Entity Framework that works with VS 2008 RTM: http://www.microsoft.com/downloads/details.aspx?FamilyId=15DB9989-1621-444D-9B18-D1A04A21B519&displaylang=en
And don't miss this little note: "Be sure to download the Entity Framework Tools December 2007 CTP as well for integration with Visual Studio 2008."