Wireless grid is a wireless network based virtual system that consists of wireless-connected different types of electronic devices and computers. It has broad application prospects in e-learning, mobile e-business, modern healthcare, smart home, wireless sensor networks and disaster management. Wireless cloud is a natural extension of wireless grid. On the basis of a literature analysis, this paper gives a category on wireless grids, and discusses the concept, characteristics and architectures of wireless grids. Then it presents a review on the existing work, mainly focusing on the issues of communication technologies, middleware and applications. At the end, the paper analyzes the open issues and lists the main research directions in this field. The survey indicates that the wireless grid and cloud is a vibrant research area.