Bonus slot features of slot machines are becoming more and more popular since the new variations became more and more popular among players. Today, you will find that casinos are offering various types of bonus features on their slot machines with special themes to draw more and more customers towards one of the oldest and still exciting casino game. The themes of these bonus slot game can differ from casino to casino. The themes might include special women slots, the free rolls, or the different type of combination for winning online slots that appeal to different crowds. So go ahead and try out these bonus slots.