Digital signage (DS) is becoming well accepted as a ubiquitous medium that can deliver and display various types of information by specifying the location and time. In this paper, we put our focus on the following two directions of DS development: (1) Networked DS: networking displays to form a large-scale open DS network that allows content providers to submit contents, and schedule, deliver, and display the contents at the right place and time, (2) Context-aware DS: displaying contents appropriate to the current status of people, places, and objects around the display, that is, changes in context. This paper gives an overview of the research being done on these issues, specifically, content scheduling, real-time content adaptation, and context sensing. Finally, some of the future challenges will be discussed.