There are many mobile ad networks available. The exact number keeps growing as new networks emerge. Some of the popular mobile ad networks include Google AdMob, Facebook Audience Network, and InMobi. These networks help businesses reach mobile users through various ad formats. Other networks like Tapjoy, Chartboost, and AdColony focus on in-app advertising. Each network has its unique features, targeting options, and pricing models. It's important to choose a network based on your goals, budget, and the audience you want to reach. As mobile advertising grows, the number of networks offering different services continues to expand.