Microsoft has just announced that the ADO.NET Entity Framework will not be shipped with Orcas (Visual Studio 2007(?) and .NET Framework 3.5). The previous news were that the ADO.NET EF would be released with Orcas, but without the designers, which would be released at some point afterwards. Finally, Microsoft has decided to ship the ADO.NET Entity Framework "during the first half of 2008 as an update to Orcas".
It was not easy for everyone to see why Microsoft was pushing two object-relational mapping products at the same time, LINQ to SQL and the ADO.NET EF, but now that only LINQ to SQL is going to make it in Orcas, it probably gives it a higher chance to be widely used. People adopting Orcas are likely to start using LINQ to SQL and not wait until the ADO.NET Entity Framework shows up.
The good news is that we cover LINQ to SQL in LINQ in Action, so we'll be able to help you to get up to speed with it :-) We do not cover the ADO.NET Entity Framework because it's not really related to LINQ, except the LINQ to Entities extension that allows (or will allow) querying the ADO.NET EF without writing Entity SQL.
Update: Microsoft finally presents its data-access strategy in a post that covers the ADO.NET Entity Framework, LINQ to SQL, LINQ to Entities, and the differences between them.
Cross-posted from http://linqinaction.net