Messy play. Anything like sand, goop, playdough, slime, water, mud.....all of the messy stuff. Put the kids outside with it and let them loose. Mine will find sticks, leaves, stones, anything laying around to add to it to extend it.

When I cook sometimes, I give the kids some rice and measuring cups/spoons ect to play with. Or flour and water in separate containers for them to mix together. It will keep them entertained for ages! And they learn so much from this sort of play- maths concepts (measuring...), science concepts (wet/dry mixtures...), language (discussing what they're doing...), imaginitive play. And above all else, it is stuff you have in the house and it is non toxic, edible and FUN!!! Yes it is messy, but cleaning is easy when you know how much they gain from it. Plus the kids love to help clean up too!

(BTW, I have recipes for playdough, goop and slime if anyone wants them.)