Small Pets DIY... Ferret ball pit made from plastic Easter eggs. I got 144 of them from oriental trading for $10 The eggs are also great for balls to roll around when you put beads or beans in them.
Ferret fun, What a great idea!
ferret play area
Cheap and would keep the ferrets occupied. Need to think where both end of the pipe go to though.
DIY Ferret Tunnel Wall - PetDIYs.com
Marshall Pet Products Pop-N-Play Ferret Ball Pit Toy at PETCO... But it would be way cooler to make it yourself
101 Ferret Games & Homemade Ferret Toys More
Pet Hedgehog... I might leave out the gems, and sub in rice for sand and some packing peanuts.
Dig box magic More
plastic tunnel ferret | FerreTrail Playground Kit Ferret Toy/Exerciser | eBay