This site provides description of a free software package - MLPowSim, that calculates power for complex random effects models. It was developed by the Centre for Multilevel Modelling - the same group that developed the LMwiN package for analysis of complex random effects models.
Bristol University | Centre for Multilevel Modelling | MLPowSim. Available at: http://www.bristol.ac.uk/cmm/software/mlpowsim/
