As a short answer:
bjam --toolset=msvc-9.0 address-model=64--build-type=complete
As a longer answer, here are my build notes for having VS .NET 2008 32-bit and 64-bit boost libraries in the same hierarchy (which is I suspect a common use case):
Build the win32 binaries
bjam --toolset=msvc-9.0--build-type=complete stage
Create the directory lib/win32
Move the contents of stage/lib to lib/win32 Remove the directories bin.v2 and stage
Build the x64 binaries
bjam --toolset=msvc-9.0 address-model=64--build-type=complete stage
Create the directory lib/x64
Move the contents of stage/lib to lib/x64 Remove the directories bin.v2 and stage
