Make a hamster maze. Here is a good one:
http://hamsterhideout.com/blog/2008/04/17/how-to-diy-a-hamster-maze/
Or you could make a "playground" like I did: fill a plastic sterilite bin a few inches deep with bedding they can dig around and burrow.
Eco Bedding for Small Pets
Kaytee Soft-Sorbent Bedding
Sprinkle flax seeds/food around for them to find. Add toys and a igloo. A great chew toy is unshelled hazelnuts.