I just answered to a request on a mailing list. It looks simple to add a folder to the inbox, but I needed some time before getting it right..
On Error Resume Next
set olApp = CreateObject("Outlook.Application")
set inbox = olApp.GetNamespace("MAPI").getDefaultFolder(6)
set temp5 = inbox.folders.add("Added by vbscript",6)
6 is for the inbox