The incredibly versatile TP tube filled with hay & string.
Mothering with Mindfulness : Schoolhouse Toys
DIY small animal platform. I would add a rail though.
DIY Hamster Treat Ball 2
DIY Toys Archives - Page 4 of 4 - BudgetBunny
Digging Tower for Hamster 255x20x245cm Small Animal Toys for Sale
Fun & Food for Gerbils the rabbits might like this also Good idea! Got to try this with my gerbil!
Image titled Make a Tunnel Playground for Your Gerbils Step 4
Toy ideas, help *pic* - Rabbits United Forum
DIY Hamster Sand Bath