Dunno much about Freelanders as such, but obvious places to look are wheel, are the nuts tight, are all the wheel weights still on, are the tyres matches, inflated correctly, not obviously losing tread ..Then look at propshaft and UJ's, then if nothing obvious take wheels off and hubs and check CV joints.
Could also be an issue with the clutch, cooling fan, fan/auxiliary belts, the gearbox, harmonic dampers, indeed it could be almost anything that's either broken or loose and is rotating unbalanced thus creating the shaking.