We just announced SharePoint 2010 preliminary system requirements at http://blogs.msdn.com/sharepoint/archive/2009/05/07/announcing-sharepoint-server-2010-preliminary-system-requirements.aspx.

To summarize:

- You should start planning for 64-bit SQL 2005/2008 and 64-bit SharePoint 2010. While this isn’t new news, it’s important to start planning for it now.

- SharePoint 2010 will require Windows Server 2008. In fact, for those of you who have installed SP2 and run the upgrade checker tool, you will have noticed this requirement.

- Browser support. SharePoint 2010 will support a wide set of standards based browsers. We will, however, be dropping support for IE 6.0. The team blog has some good Q&As that go into more detail.

Christophe Fiessinger recently reminded me of some good related content. Specifically the following TechNet articles:

Advantages of 64-bit hardware and software (Office SharePoint Server 2007)   This planning article describes the many advantages of using 64-bit hardware and software when setting up SharePoint servers.

Migrate an existing server farm to a 64-bit environment (Office SharePoint Server 2007)   This article provides best practice guidance and detailed instructions for moving an existing server farm to a 64-bit environment.