The Data Platform Team at Microsoft blogged about this already:
http://blogs.technet.com/dataplatforminsider/archive/2009/09/03/get-a-free-copy-of-sql-server-2008-standard-edition.aspx
If you attend PASS Summit 2009, you can receive your very own (Not for Resale) copy of SQL Server 2008 Standard for free. Add this to the fact that you get to attend 168 session dedicated to SQL Server, as well as get free assistance from the CSS and SQLCAT teams for your most difficult problems and even pick the brains of Microsoft Team members and MVP’s at the Ask the Experts Area, and you can’t lose by attending PASS Summit 2009.