If you've installed the February 2008 release of the Web Client Software Factory and, when building your first web app, you get an error similar to
"Cannot find System.Data.DataSetExtensions blah blah blah
then check the dll which is located at C:\Program Files\Reference Assemblies\Microsoft\Framework\v3.5\; if it has a version of 3.5.20706.1 then you did what I did. You installed the WCSF on a machine which has the beta version of Visual Studio 2008 on it. You need to uninstall that version and load the release version of VS 2008 where the version number for the above dll is 3.5.21022.8; or at the very least you'll have to install the release version of the .Net 3.5 framework redistributable.