This focus issue presents a collection of research papers from a broad spectrum of topics related to the modeling, analysis, and control of mechanical oscillators and beyond. Examples covered in this focus issue range from bridges and mechanical pendula to self-organizing networks of dynamic agents, with application to robotics and animal grouping. This focus issue brings together applied mathematicians, physicists, and engineers to address open questions on various theoretical and experimental aspects of collective dynamics phenomena and their control. Published by AIP Publishing.[http://dx.doi.org/10.1063/1.4967727]Collective behavior in mechanical systems was discovered by the Dutch scientist Christiaan Huygens around 1665. 1 In the Huygens' setup, two pendulum clocks, hanging from a wooden beam, showed an "odd" symmetry and ended up oscillating in perfect anti-phase. [2][3][4] In recent years, collective dynamics has become an important topic with applications in a wide spectrum of biological and technological networks, including multi-robot teams, complex mechanical structures, and pedestrian bridges. This focus issue aims at the largely unexplored area of mathematical analysis and modeling of cooperative networks arising from different applications in mechanics and beyond. This highly interdisciplinary issue presents new research contributions which integrate knowledge from different disciplinary areas in applied mathematics and engineering, including stability theory, information theory, piecewise smooth and stochastic dynamical systems and networks, graph theory, classical mechanics, and bio-mechanics. We hope that this collection will contribute to further igniting interest in collective dynamics of mechanical oscillators and promoting interdisciplinary collaborations.