GameUp is a wonderful free site for educational games as part of a section of BrainPop. Games are on a variety of subjects and are even for PreK-3rd grade (BrainPop Jr.) or ESL games. These cartoon/animated interactive games are very easy to use and intertwine nicely w/ BrainPop's popular/successful lesson plans and quizzes.
I highly recommend checking out GameUp by clicking here!!!