This post contain my personal favorite downloads in this month.
Sandcastle - September 2006 Community Technology Preview (CTP)
Sandcastle enables managed class library developers throughout the world to easily create accurate, informative documentation with a common look and feel.
Visual Studio 2005 Team Edition for Database Professionals CTP 5 - Beta
Tools for building SQL databases in a managed project environment with support for versioning, deployment, unit testing, refactoring, and off-line SQL development.
Windows Software Development Kit for September CTP of Windows Vista and .NET Framework 3.0 Runtime Components
The Windows SDK contains pre-release documentation, samples, and tools designed to help you develop Windows applications and libraries using both Win32 and .NET Framework 3.0 technologies targeting Windows Vista.
Microsoft Exchange Server 2007 Beta 2 Help (September Refresh)
This download contains the latest standalone version of Microsoft Exchange Server 2007 Beta 2 Help.
Windows Base Operating System Management Pack for MOM 2005
This management pack monitors for conditions that adversely affect the availability, reliability, performance, configuration, and security of Windows Server 4.0, 2000, 2003, and 2003 R2 operating systems.
Microsoft Forefront Security for SharePoint (Beta)
Forefront Security for SharePoint helps businesses protect their Microsoft Office SharePoint Server 2007 and Windows SharePoint Services 3.0 from viruses, unwanted files, and inappropriate content.
BizTalk Server 2006 Adapter for Microsoft Dynamics CRM 3.0
This download enables integration between Microsoft Dynamics CRM and non-Microsoft Business applications.