The Windows SDK for Vista has been finalized and is now available for download:

Web install: http://www.microsoft.com/downloads/details.aspx?FamilyId=C2B1E300-F358-4523-B479-F53D234CDCCF&displaylang=en
ISO: http://www.microsoft.com/downloads/details.aspx?FamilyId=7614FE22-8A64-4DFB-AA0C-DB53035F40A0&displaylang=en