Microsoft released a Microsoft SQL Server 2008 Feature Pack, August 2008 page which includes a collection of stand-alone install packages that provide additional value for SQL Server 2008. Strangely, Report Builder 2.0 is excluded and nowhere to be found since the RC0 page has been taken offline.
Update 8/7/2008:
A RC for Report Builder 2.0 feature pack will be available for download toward the end of August