Just my 2c to agree with sibling posts. For some reason, moving boxes are big on the local Gumtree Freebies, and after my son found out about this, every couple of weeks I get asked to get some boxes for him to play with (which typically gets retired a weekend or two later).

Sure, they take up more space than Lego or Mecards or Beybaldes, but absolutely can't beat them for entertainment value.