I have found the bin bag is the answer. I ask them to clean up. If they ignore me i throw their things out since they obviously do not treasure them enought to put them away. I once threw out a large pile of DH's clean clothes because I had washed, dried and folded them neatly and he dumped the pile on the floor rather than put them in his drawers. I will admit this tactic is far more effective with the younger children than the grown up one, but I find throwing their dropped bits of crap at them works a treat as well.