Playtime is a great opportunity to bond with your pet. Take advantage of this time and encourage social behaviour. Hamster balls are widely available, however some people are against them; it is your desicion whether or not you use a hamster ball, but here are some tips to help you decide:
Make sure your hamster is never in the ball for more than 20 minutes at a time, they will get tired and dehydrated.
Make sure you have a clear plastic ball, hamsters are shortsighted and if a ball is dark they can be incredibly frightening to your pet.
Playpens are large areas where you can get out larger hamster toys, however you will still need to supervise your pet at all times. Hamsters can escape very easily.