Single spins associated with nitrogen-vacancy (NV) defects in diamond have emerged as a promising and versatile experimental platform for quantum information processing. They can be used as nodes in optically connected quantum networks, as sensors for magnetic imaging with sub-micron resolution, for detecting and engineering quantum states of nano-mechanical oscillators, and even as probes in biological systems. Our group has demonstrated improvements to dynamic range and sensitivity of magnetometry using phase estimation algorithms, and carried out electron paramagnetic resonance detection and spectroscopy of single Cu ions on the diamond surface. I will also discuss a unique system in our lab where we magnetically trap and laser cool diamond microcrystals under high-vacuum room-temperature conditions for the first time, and discuss the path forward to observing quantum superpositions of macroscopically separated motional states.