Thanks to Adam Thurgar for the tip: Microsoft has released Service Pack 5 for SQL Server 6.5 in the form of a 13 MB download for both Intel and Alpha platforms. SQL Server service packs are cumulative, so Service Pack 5 includes all of the fixes from previous packs as well as so new, yet unknown fixes. Since SQL Server 7.0 was just recently released to manufacturing, I'd expect that this will be the last service pack for 6.5.
SQL Server 6.5 Service Pack 5 includes some Year 2000 fixes and support for the Euro currency symbol. It also includes an optional install of Microsoft Data Access Components (MDAC 2.1), the version of MDAC that comes with SQL Server 7.0.
To download the service pack, please visit the Microsoft FTP site