(left photo) A roll of cardboard tied with cotton string (I simply tore a cardboard box into strips) is a favourite chew toy plus fun to push and roll around the room.
Blankets, soft toys and pillows are fun for exploring and pushing around; some buns have their own little blanket which they put where they want. For one of our house rabbits, it's an old jumper of mine.
A wicker basket provides hours of entertainment and chewing (only use natural ones - not painted or varnished); note the offcut of pine wood for chewing in the background, which discourages chewing of wood furniture already in the room.
other home made toys: