The concept of a smart city has recently gained attention in academic, industry, and governments. Smart cities could be considered as urban areas that use data collection sensors and digital technologies which cooperate to create benefits for citizens in terms of well being, inclusion and participation, environmental quality, and intelligent development. Smart city vendors provide software systems to support application developers, city managers, urban planners, and policy-makers in designing, implementing, deploying, and managing smart city applications for an effective urban development and management. Although there exist a variety of smart city software systems, their benefits and limitations are still unknown. In this paper we review smart city vendors and we provide insight into their software systems for smart cities. Thus, we come up with a good entry point, and here survey a large amount of information to help developers, city managers, urban planners, and policy-makers to take better decisions when choosing smart city software systems.