What to do with your kids old but good stuff

So what do you do with your kid's old stuff; toys, cloths, shoes, used text books, story books that he won't read anymore cos he's a big boy now and " mummy i've read it already!!!"??

We used ours for a Flea Market to raise funds for African children in need of Sanitation and sustainable drinking water, and we raised alot!!
So spring clean and resell.....but only the good stuff :)