In addition to carrying a quantized electrical charge, electrons also possess a quantized angular momentum, or spin.  In ordinary charge-based electronics, the spins are usually randomly oriented and they do not play a role in device function.  However, in the last ten years there have been significant advances in understanding how to control electron spins in useful ways.  Spin currents can now be used, for example, to apply torques within magnetic memory devices that are more than 1000 times stronger than charge-current-generated magnetic fields.  I will discuss some of this progress, with an emphasis on recent discoveries that magnetic devices can be manipulated with record-breaking efficiencies using strong spin-orbit coupling in heavy metals and topological insulators.