Here are some ideas for a user friendly guinea pig play pen

List of requirements

Plastic shower curtain lined with a blanket

Cube playpen made with 17 cubes which are loosely connected with cable ties (You don't want to cable tie it too tight as you want to be able to fold it away for storage) one over laps so it can be bulldog clipped together to use and then folded away for easy storage after.

And then comes the toys.

Play tunnel 4" plumbing pipe available in many configurations

Litter box/ hay box cat litter box  cut down on one side lined with several layers of newspaper then add the hay

Wood tunnel Fiddle sticks large one shown available from pet stores

Other great toy ideas

Grocery/shoe boxes

Paper lunch/grocery bags

Toilet tubes or kitchen roll tubes stuffed with hay

There are Many ferret and cat toys that guinea pigs love to play with. There are also wooden hanging toys designed for birds are a great idea to hang in the cage. (be careful leaving toys with small pieces in with a piggy that chews as this could present a choking hazard)

Do not use exercise wheels which can cause back injuries or large exercise balls as these too can cause crippling injuries to a guinea pigs back. 

Outdoor Play

Guinea pigs love having a chance to get outside and graze on some fresh grass. With that in mind here are some safety rules to keep in mind.