SQL Server 2005 SP1 Released!
Microsoft has already - yes, already, as in 6 1/2 months after initial release - released SQL Server 2005 SP1!
The main page for SP1 is part of the SQL Server site but doesn't give a lot of detail. The press release on SP1 is vaguely helpful, including the fact that Database Mirroring is in fact now released. The knowledge base article (913090, "A list of the bugs that have been fixed in SQL Server 2005 Service Pack 1") is much more helpful.
On a related note, they have also released the SQL Server 2005 Feature Pack, which is really a collection of downloads in one place for client drivers (e. g. the Native Client, Analysis Services Client, etc.) as well as other useful tools.
You can also get updated Express tools and installation sets, updated samples and sample databases, the December, 2005 update of Books Online (if you don't have it yet), or just the Readme files for SP1.