Firstly, the simple stuff. If you've not come across them yet then the documentation for Visual Studio 2008 Service Pack 1 is up here;

Home Page

Entity Framework

Data Services

I also find this page extremely useful as I've been asking for it for many months. It lists the supported mapping scenarions for Entity Framework;

http://vs2008sp1docs.msdn.microsoft.com/en-us/ms439043.aspx

Now, the tricky bit. I had quite a lot of trouble installing Visual Studio 2008 Service Pack 1. Here's what I ended up doing;

I followed the instructions very carefully and uninstalled the necessary Hotfixes, Silverlight tools and so on. I also uninstalled the ASP.NET 3.5 Extensions Preview and the Entity Framework preview bits and Expression Blend 2.5 March Preview.

Then I installed Sp1.

First Time. It failed. I had missed a hotfix which I didn't see listed on the instructions. I uninstalled the hotfix.

Second Time. It reported failures on the way through but reported success at the end. I tried a new ADO.NET Entity Framework project and found it wouldn't build because of a [DataContractAttribute(IsReference=True)] which I figured must be an addition to the DataContract stuff that hadn't been installed properly.

Third Time. I uninstalled the Service Pack. Repaired Visual Studio. Installed the Service Pack. It worked. No failures at all. However, I now had no "ADO.NET Entity Framework" project type and no "ADO.NET Data Service" project type.

I read this stuff which seemed to show that other people are having the same problem but the ultimate solution seemed to be "reinstall".

Fourth Time. I uninstalled Visual Studio 2008 and everything I could find relating to it including lots of SDKs, MSDN Library, everything. I obliterated the Visual Studio 2008 folder. I know I'll regret this at some point in the future but I'm getting a bit desperate. Then I installed VS 2008 again from scratch.

VS 2008 installation failed :-( on the SQL Server Publishing Wizard.

I tried a repair on VS 2008. It worked.

I installed Service Pack 1. It worked.

So, I got there in the end but it took a bunch of work - "your mileage may vary" as they say.