SQL Server 2008 Express (basic) and SQL Server Compact 3.5 SP1 are now live on the Microsoft Download Center.
The English link for SQL Server 2008 Express (basic) is: http://www.microsoft.com/downloads/details.aspx?FamilyId=58CE885D-508B-45C8-9FD3-118EDD8E6FFF&displaylang=en.
SQL Server Compact 3.5 SP1 was delivered with SQL Server 2008 and Visual Studio 2008 SP1 with these key new features. It’s available at http://www.microsoft.com/downloads/details.aspx?FamilyID=dc614aee-7e1c-4881-9c32-3a6ce53384d9&displaylang=en.
The features are:
ADO.NET Entity Provider
Case Sensitive Collations
64bit Support, including the ability to include both 32bit and 64bit privately within the users app
Sync Services for ADO.NET client provider rounded out for the Windows Mobile platform