While configure could find my Boost installation, CMake could not.
Locate FindBoost.cmake and look for LIBRARY_HINTS to see what sub-packages it is looking for. In my case it wanted the MPI and graph libraries.
# Compute component-specific hints.
set(_Boost_FIND_LIBRARY_HINTS_FOR_COMPONENT "")
if(${COMPONENT} STREQUAL "mpi" OR ${COMPONENT} STREQUAL "mpi_python" OR
${COMPONENT} STREQUAL "graph_parallel")
foreach(lib ${MPI_CXX_LIBRARIES} ${MPI_C_LIBRARIES})
if(IS_ABSOLUTE "${lib}")
get_filename_component(libdir "${lib}" PATH)
string(REPLACE "\\" "/" libdir "${libdir}")
list(APPEND _Boost_FIND_LIBRARY_HINTS_FOR_COMPONENT ${libdir})
endif()
endforeach()
endif()
apt-cache search ... I installed the dev packages since I was building code, and the dev package drags in all the dependencies. I'm not so sure that a standard Boost install needs Open MPI, but this is OK for now.
sudo apt-get install libboost-mpi-dev libboost-mpi-python-dev
sudo apt-get install libboost-graph-parallel-dev