There are probably a few others but saw these while searching for an issue I have.
win2k3 (16) -> windows-server-2003 (1580)
windows-server-2003-r2 (10) -> windows-server-2003 (1580)
windows-server-2008-sp2 (4) -> windows-server-2008 (1413)
Those questions tagged [windows-server-2008-sp2] probably relate directly to issues with Service Pack 2, so I don't know if it would be appropriate to genericise that tag. However, [windows-server-2008] should certainly be added so they can be found in a more generic search.