Microsoft PST Capture is a neat free tool that helps you search your network for .PST files and then import them into your Exchange server.
With the PST Capture Agent you can locate users .PST files and import them into Exchange.

You can download the tool here: http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=28767

If you want to read more:
http://technet.microsoft.com/en-us/library/hh781036.aspx
http://blogs.technet.com/b/exchange/archive/2012/01/30/pst-time-to-walk-the-plank.aspx