Windows Server Update Services, a.k.a WSUS is live - go download here. WSUS is the next version/evolution of SUS. SUS was going to named SUS 2.0, then Windows Update Services (WUS).
MSDE2000a, WMSDE, or SQL Server 2000 with SP3 is a pre-req, as is BITS 2.0. Get BITS 2.0 at -- http://support.microsoft.com/kb/842773
The deployment guide is here.
Gord's Q&A is here.