SQL Server Express installation and blog
Like others, I have also installed the new SQL Server 2005 Express version found here: http://lab.msdn.microsoft.com/express/sql/. So far, I like what I see. I will report more as I do some testing (and playing -) ).
There is also a new blog available from the SQL Server Express team (subscribe to the RSS).
They already have a post about the differences between SQL Server Express and MSDE.