MailRaider - open Outlook .msg files on your Mac
One of the more frustrating things I found when moving from Windows to a Mac in a business environment was receiving email messages that contained other messages as attachments. This is a fairly common thing for Outlook users to do, and it doesn't usually cause problems because Outlook can happily open those messages. It's not very good email etiquette and you should avoided doing it if possible (forwarding the message makes it possible for the receiver's email program to index and search the contents), but there are times when it makes sense -- such as when forwarding a batch of messages at once.
The problem is that the Mail app that comes with all Macs unfortunately isn't capable of opening Outlook's .msg files. If you use a Mac and regularly receive messages from Outlook users, it's likely you've run into this problem at some point.
45RPM Software created MailRaider to solve just this problem. It's a free app that does one thing, and one thing well: makes .msg files created with Microsoft Outlook viewable on a Mac, including any included attachments. Formatting may be lost, but typically that's not a huge issue.
One interesting aspect of MailRaider is that the developer has pulled out the code that he uses to read the mail messages, and has turned it into a framework he calls MOLE. MOLE is a free framework for developers to use that need to read Microsoft OLE documents on a Mac.
There are other ways to read Outlook messages on a Mac, but MailRaider's price (free) and simplicity are definitely compelling.