Carlos Quintero of MZ-Tools has started his blog subtitled as Visual Studio Extensibility: macros, add-ins, SDK packages. You may already know Carlos from several newsgroups related to VS extensibility
microsoft.public.vstudio.extensibility
microsoft.public.vsnet.ide
MSDN: Visual Studio Extensibility.
Or from vsnetaddin group which discusses how to write Visual Studio.NET add-ins, wizards, and macros using the IDE automation model and VSIP interfaces.
Or you have seen his great set of articles for add-in developers on his site.
And of course, almost every VS user knows his MZ-Tools add-in.