Microsoft SQL Server SP1 has been released on the 16 of March as a Community Technology Preview
This service pack can be used to upgrade all editions of SQL Server 2005 to SP1 except Express Edition. You must use Microsoft SQL Server 2005 Express Edition (SQL Server Express) Service Pack 1 (SP1) to upgrade instances of SQL Server Express to SP1. SQL Server Express SP1 can be obtained from the Microsoft Download Center Web site. This service pack cannot be applied to any pre-release versions of SQL Server 2005.
Links to the service pack and other information
Service pack Readme file
Express version download
List of fixes
SQL 2005 Forums