Due to a snafu, the TFS docs were inadvertently removed from the VS2008 SDK.  The situation has been remedied.  You will find the latest version of the TFS SDK docs here: http://msdn2.microsoft.com/en-us/library/bb130146.aspx.  Many of you probably never noticed - all the better :)  However I did get quite a few inquiries about it.  Thanks for your patience.