Windows 2003 SP2 is out. This service packs fix a lot of problems in IIS 6.0, Networking, Terminal Server and more.
Be aware that there are also many fixes for .NET Framework 1.1 which are not available, as far as I know, with a separate service pack for .NET Framework. This may create a lot of interoperability problems if you have deployed applications on both Windows XP and Windows 2003 Server.

List of updates in Windows Server 2003 Service Pack 2

Download Windows Server 2003 SP2 (150 MB)