Nitrogen vacancy (NV) centers in diamond offer a prime opportunity for coherently controlling the state of a quantum system. The spin state of the NV center can be manipulated with a sequence of optical and microwave pulses, and exhibits long coherence times even at room temperature. It can either be isolated from the environment for quantum information processing tasks or be used as a sensor of external electric or magnetic fields. Shifting the NV center's energy levels with a vector magnet allows it to operate at frequencies ranging from DC up to 20 GHz. The NV center's high degree of tunability, both in terms of its frequency range as well as its sensitivity to the environment, make it a versatile system when coupled with an experimental setup that can fully exploit its properties.