Yesterday Microsoft made an annoucement about a number of features that are being released with Exchange 2010 Sp1 which can be found here http://msexchangeteam.com/archive/2010/04/07/454533.aspx. One feature that a number of people have been asking for is the ability to add a personal archive to Outlook 2007, Microsoft has heard from the masses and will be adding this to Outlook 2007 in a future update.