A few days ago I sat for the beta exam 70-561 .NET Framework 3.5 ADO.NET. This is the second exam that I've taken for the new .NET 3.5 certifications generation; at the end of last year I took 70-503 WCF's exam and I recently got the results with a happy end for me :)
In 70-561 exam besides traditional topics such as ADO.NET connected data(Commands, DataReaders, etc) and ADO.NET disconnected data (DataSets, DataTables, etc), there is plenty of new stuff that you'd better be familiar with if you want to pass! One of those things is LINQ and LINQ to SQL, which I didn't find particularly difficult maybe cause I've had the chance to work with it.
If you are not familiar with LINQ to SQL, my buddy Sidar came up with a great introduction post and Scott Guthrie has a very nice series of posts that you don't want to miss out.
Another new topic, (at least for me) was Synchronization services. Maybe it's because I've never used it, but questions about Synchronization Services were by far the most difficult for me! You can find here a bunch of demos for the Synchronization framework that you might find useful.
The last but not the least is the Entity Framework which is still in beta... That's one of the disadvantages of taking beta exams, you are sometimes supposed to have knowledge and experience in technologies that haven't been available long enough... I won't complain though, beta exams do have some advantages (Did I mention that they are free?:)) You can find some code samples for EF Beta 3 version in CodePlex.
The beta period for this exam and ASP.NET exam have been extended until the 5th of May, so if you haven't sat for it yet and you want to take it, hurry up and check Gerry's certification blog!