I recently had the need to look up the email address of an acquaintance that I misplaced years ago. During my time working with this person, I, thankfully, made routine backups of the local cache of my exchange server profile. I did this in case the server data happened to become corrupted or ruined since the local cache used by outlook is a full copy of the data stored by the server, given all content is set to be downloaded during a synchronization. Making the backup is typically as simple as copying the appropriate *.ost file from the “%USERPROFILE%\My Documents\Outlook Files\” folder (though, you should make sure to disconnect from the exchange server and completely close Outlook to unlock the file if it is in use or the primary profile).
Unfortunately, this file is not meant to be used as a backup, nor is Outlook capable of importing it. After about 20 minutes of Google-fu and failed solutions (usually meaning not freeware or simply useless advice), I came across this blog post describing two programs called Kernel PST Viewer (description, download) and Kernel OST Viewer (description, download). The second program caught my attention, and it turned out to be just what I needed. While it is somewhat functionally limited, it does exactly what it is expected to do and allows one to view the contents of an *.ost file in a simple and well organized layout.