Need help troubleshooting Outlook 2007 performance issues? Well, this link will help you do just that to rule out the specific things that might be causing significant performance degradation.
Performance tips for deploying Outlook 2007 http://technet.microsoft.com/en-us/library/cc179071.aspx
Here is a hidden little gem (Messaging guide for Office 2007) that has all kinds of useful information in it, but unfortunately you cannot find it since it is posted as a document and not as a nicely formatted HTML page so our Indexing services can consume it.
Downloadable book: Messaging guide for the 2007 Office release http://technet.microsoft.com/en-us/library/cc179109.aspx