The SQL Server 2005 SP1 CTP has been available since last Wednesday, here is the URL http://www.microsoft.com/downloads/details.aspx?FamilyID=39ebef74-1c29-49fe-8221-c94f2b52f6c6&DisplayLang=en and interestingly enough, there is also an SP1 CTP update to the Books Online documentation which is here http://www.microsoft.com/downloads/details.aspx?familyid=19db0b42-a5b2-456f-9c5c-f295cdd58d7a&displaylang=en.

This is a direct link to the readme file for the SP1 CTP http://download.microsoft.com/download/8/3/8/838be27d-e469-43e5-8ea0-e67c7159ac12/ReadmeSQL2005SP1.htm

And finally, here is a list of the bugs which have been fixed in this build http://support.microsoft.com/kb/913090