SQL Server 2005 SP3 is now available for download and includes the following updates:
- Roll-up of Quick Fix Engineering (QFE) updates completed since SQL Server 2005 SP2, as well as fixes to critical issues reported through the SQL Server community. Per revised servicing strategy for SQL Server releases, SP3 does not introduce major new features.
- Feature Pack for SQL Server 2005 SP3 has been refreshed along with this release.
- SP3 can be used to upgrade from any previous instance of SQL Server 2005
- For customers who will be upgrading from SQL Server 2005 SP2 CU#10 or SP2 CU#11, you will have to install the latest CU on SP3 after upgrading to SP3 release to get all the fixes.
- SP3 applies to:
- SQL Server 2005 Enterprise Edition
- SQL Server 2005 Enterprise Evaluation Edition
- SQL Server 2005 Standard Edition
- SQL Server 2005 Workgroup Edition
- SQL Server 2005 Developer Edition
Note: Service Pack 3 includes SP2 CU 1 to 9, therefore If you are upgrading from SQL Server 2005 SP2 Cumulative Update 10 or from SQL Server 2005 SP2Cumulative Update 11, you must apply a post-SP3 cumulative update after you upgrade to SP3 to obtain all the fixes.
As always make sure to test the release in your development environments before applying to production 
