OutlookSpy

OutlookSpy just added support for the Outlook Integration APIs. If you don't know what OutlookSpy is (from their website) ...

OutlookSpy is the ultimate Outlook developer tool. Integrated directly into Outlook, it provides fast and convenient access to all Outlook Object Model objects, lets you examine values of the properties, call functions, browse object hierarchy and monitor Outlook events. CDO is supported too!

If you're developing on Outlook a tool like this (such as MdbView) is a necessity.