The Exchange Mailbox Merge Wizard (or Exmerge for short) is one of the most important tools in the Exchange administrator's toolbox. Basically, it is a GUI (and/or script) based tool that can copy or move messages, rules and forms from an Exchange mailbox into an Outlook .PST file. And it can copy messages from an Outlook .PST file back to an Exchange mailbox.
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=429163ec-dcdf-47dc-96da-1c12d67327d5
