I promised an update on SQL Express availability in my last post about the release of SQL Server 2008 so here it is. SQL Server 2008 Express is now available along with the release of the .NET Framework 3.5 SP1, which is a prerequisite and Visual Studio Express SP1. As I mentioned, there are two more editions of SQL Express on the way. There are a number of prerequisites for SQL Server 2008 that you will have to install on your own before installing SQL Express.
The article continues at http://blogs.msdn.com/sqlexpress/archive/2008/08/11/sql-server-2008-express-is-now-live.aspx