Visual Studio 2008 SP1 doesn't provide any language pack prerequisite for the .NET Framework 3.5 SP1.
My research results are: it should be easy to create a custom bootstrapper package that installs a language pack. I've downloaded the Bootstrapper Manifest Generator. It's really a nice tool to create custom packages, but I don't know what are the correct parameters (e.g. reboot mode, installation time and size, install conditions, exit codes, etc.) for a language pack package.
Are there ready-to-use bootstrapper packages for .NET Language Packs?
Best Answer
This page details deployment of the .NET Framework 3.5
http://msdn.microsoft.com/hi-in/library/cc160716(en-us).aspx
Since you are working with various languages you should use the dotnetfx35setup.exe executable to do the install, since it detects the proper language packs and downloads them. You'll have to do some looking to find the proper HomeSite URL to use to download it, but it shouldn't be hard to find.
That page should detail all the command line switches you will need to get it up and running.
The Bootstrapper Manifest Generator is nice, but seems to sometimes have issues. You will probably want to look at the existing English bootstrapper for the .NET Framework 3.5 as a template for your multi-language one.
About the exit codes, I am fairly certain the dotnetfx35setup.exe web bootstrapper uses the same ones as the dotnetfx35.exe one.