Real Simple is full of great ideas. Check out the Fall Organizing series.
So far mum and I have tackled Little Guy's wardrobe. I had been throwing all the "too-small" clothes up onto the top shelf to the point where it was hazard if you opened the doors. Now we have two big rubbish bags of clothes to pass on and trash.
We've also done the toy cupboard. I had to move some things around so mum could have her own space while she's here. Moving around again involved throwing stuff into a cupboard and quickly closing the door before the avalanche. Now we've got a lovely big bin of baby toys to pass on to my kids' new baby cousin (due in December).
Next on the list, our shed which is stuffed to the point of bursting since we had the typhoon which did not eventuate.