The (missing) Visual Studio 2008 SDK Reference
While I don't write VS packages with the SDK, sometimes I need to use the SDK documentation to get an interface/service (most of the time to answer some question in the forums, or to do something that can't be achieved with the automation model EnvDTE for add-ins). Since I don't know by heart the name of all interfaces, I use the following page to search for an interface with some word in the name:
Notice that the page belongs to Visual Studio 2005 \ Visual Studio \ Visual Studio SDK \ Reference \ Visual Studio Platform Reference (you can navigate the tree to the left). For some reason, the page still displays the warning "[This topic is pre-release documentation and is subject to change in future releases. Blank topics are included as placeholders.]" but I can live with that.
When I navigate the tree to locate the equivalent for Visual Studio 2008, I never find it, so today I investigated a little more and I found the following page:
Visual Studio SDK Reference
which applies to VS 2008 and where the "Visual Studio Platform Reference" link is not a link (neither the Managed Package Framework Reference link), and for that reason I guess it doesn't appear in the tree too. The page still shows the warning [Note: This topic is pre-release documentation and is subject to change in future releases. Blank topics are included as placeholders.] and apparently is not updated since November 2007.
So, until the VS 2008 documentation is updated, you have to use the VS 2005 SDK reference documentation.