Studies of galactic rotation have suggested the presence of Dark Matter, but it's effects do not seem to affect orbital mechanics at solar system scales where we can make very precise observations (the Pioneer Anomaly may be our first contraindication of this). However, gravitationally bound systems at intermediate scales have been studied for centuries:
binary stars. Has anyone considered the study of multiple star systems as a probe into Dark Matter distribution in the interstellar environment? Are there any anomalous observations of binaries which might be explained by taking Dark Matter perturbations into account? This might help settle once and for all the issue of whether Dark Matter is indeed ordinary matter which is invisible, some new type of matter altogether, or if it not matter at all but a flaw in our understanding of gravitation. It would also make double star astronomy fashionable again with researchers!