To be truly effective, online learning must facilitate the social process of learning. This involves providing space and opportunities for students and faculty to engage in social activities. Although learning management systems offer several tools that support social learning and student engagement, the scope, structure, and functionality of those tools can inhibit and restrain just-in-time social connections and interactions. In this teaching tip, we describe our use of Twitter to encourage free-flowing just-in-time interactions and how these interactions can enhance social presence in online courses. We then describe instructional benefits of Twitter, and conclude with guidelines for incorporating Twitter in online courses. (Contains 1 figure.)