Vehicular Ad-hoc Networks (VANETs) have been recently attracting an increasing attention from both research and industry communities. One of the challenges posed by the study of VANETs is the definition of a generic mobility model providing an accurate, realistic vehicular mobility description at both macroscopic and microscopic levels. Today, most mobility models for vehicular studies only consider a limited macro-mobility, involving restricted vehicles movements, while little or no attention is paid to micro-mobility and its interaction with the macro-mobility counterpart. On the other hand, the research community cannot have access to realistic traffic generator which have not been designed to collaborate with network simulators. In this paper, we first introduce a classification of existing methods for the generation of vehicular mobility models, then we describe the various approaches used by the community for realistic VANET simulations. Finally, we provide an overview and comparison of a large range of mobility models proposed for vehicular ad hoc networks.