It is currently available for download at http://msdn.microsoft.com/vstudio/support/vs2005sp1/

A beta version of Visual Studio 2005 SP1 Update for Windows Vista Beta is also available for download. With that Visual Studio 2005 will be supported on Windows Vista, and applications written with .NET Framework 1.1 and .NET Framework 2.0 runtimes will continue to run on Windows Vista.