The public beta will be available on November 2009. Register at following location to access the software:

http://sharepoint2010.microsoft.com/try-it/Pages/Trial.aspx

Watch the SharePoint Conference 2009 keynote video

http://www.mssharepointconference.com/pages/default.aspx

SharePoint 2010 overview @ product group blog

http://blogs.msdn.com/sharepoint/archive/2009/10/19/sharepoint-2010.aspx

SharePoint 2010 (Beta) Developer Center

http://msdn.microsoft.com/en-us/sharepoint/ee514561.aspx

TechNet information for ITPro (install, upgrade….)

http://technet.microsoft.com/en-au/sharepoint/ee263917.aspx

And note that the external SharePoint Product site has the latest content

http://sharepoint.microsoft.com/Pages/Default.aspx