Radiation shielding analysis is a crucial process in the spacecraft and space instrument development cycle. A number of dedicated tools have been developed in the last decades for the study of the effects of radiation on materials and instruments in space. We present here a set of detailed analyses based on Monte Carlo radiation transport simulations, and new tools for space applications, both based on the Geant4 simulation toolkit, developed as part of the European Space Agency (ESA) activities in the Geant4 collaboration. Finally we present some activities initiated by ESA for the creation of a Geant4 space users' community.