The release candidate for Silverlight Tools for Visual Studio is currently available for the English version of Visual Studio only.  Users of non-English Visual Studio can still use this Silverlight Tools release candidate if they install the English version of Visual Web Developer Express with SP1 which is a FREE download.

http://www.microsoft.com/express/download/

Note, that installing Silverlight Tools RC0 on a machine with VWD Express SP1 ENU and VS 2008 SP1 non-ENU will allow Silverlight 2 development on VWD Express SP1 ENU only.  Neither Silverlight 2 Beta 2 nor Silverlight 2 RC development will be possible on VS2008 SP1 non-ENU until the final version of Silverlight Tools is released for the language specific Visual Studio version installed.