Last week Microsoft released Service Pack 3 for SQL Server 2005. Just in time for Christmas and not a moment too soon from my perspective with a lot of Cumulative Updates (11 to be exact), and a critical security fix bundled up inside as well...
The Service Pack is relevant to all supported server platforms (IA64, x64 & x86), oh and express edition too...
The Service Pack is cumulative, and it upgrades all versions of SQL Server 2005 to SP3 (9.00.4035)
I do like the CU and SP methodology, but I'd really like to see Service Packs released more frequently allowing us to stabilise on robustly tested bases every 3-6 months rather than every 1 year plus. This is of course a "near" perfect world senario as I couldn't account for how intensely complex the testing and resourcing coordination is when you want to certify fixes and features that are interdependant between SQL Core, Tools, AS and RS etc..!
On this "complexity and coordination" thread, Cumulative update 1 for SQL Server 2005 Service Pack 3 has also been released, as it encapsulates hotfixes that were made to SP2 CU's 10 & 11 that did not make it into the testing cycle for SP3... Its your call whether or not you make your next base SP3+CU1 or just vanilla SP3...
Information about SQL Server 2005 SP3 CU1
For detailed info on the Cumulative Update and Service Pack strategy see "Understanding Incremental Servicing Model for SQL Server"
FYI also: SQL Server 2005 Builds released after SP2