Nuclear magnetic resonance (NMR) spectroscopy provides detailed understanding of the nature and extent of protein dynamics on physiologically important timescales. We present recent advances in the combination of NMR with state-of-the-art molecular simulation that are providing unique new insight into the motions on timescales from nanoseconds to milliseconds. In particular, we focus on methods based on residual dipolar couplings (RDCs) that allow for detailed mapping of the protein conformational energy landscape. A novel combination of RDCs with accelerated molecular dynamics allows for the development of ensemble representations of the underlying Boltzmann ensemble.