Small satellites, like popular nanosatellite platforms called CubeSats, are suitable for formation ying missions because of their modular nature and low cost. This paper presents a review of thirty-nine missions, using multiple small satellites, in various stages of development. These missions are categorized based on their mission type, mission status, number of satellites, leading organization, funding source, and requirement for constellation or formation ying. We conclude that Earth science related missions are the most popular, while most multi-satellite missions only require a constellation. Although six missions aim to demonstrate formation ying capability in space using two to three small satellites, there are currently only two formation ying missions planning to use four or more small satellites.