Vehicular Networks are receiving a lot of attention due to the wide variety of services they can provide. Their applications range from safety and crash avoidance to Internet access and multimedia. A lot of work and research around the globe is being conducted to define the standards for vehicular communications. These include frequency allocation, standards for physical and link layers, routing algorithms, as well as security issues and new applications. In this paper we review the standardization work and researches related to vehicular networks and discuss the challenges facing future vehicular networks.