Rapidly rotating solar type stars display varying amounts of chromospheric emission in their Balmer lines. The profiles of these lines often display rapid variability. Since the mid-1980s, high-cadence echelle spectroscopy of numerous such stars has revealed that some of the variability is caused by concentrations of neutral hydrogen, trapped in the stellar coronal magnetic field at distances up to a few stellar radii from the rotation axis. In this paper we review the observations and the tomographic techniques that can be applied to mapping these "slingshot prominence" systems. We discuss the possible mechanisms for formation and mechanical support of these condensations, in the light of recent efforts to map 3-dimensional stellar coronal magnetic fields and X-ray emission measure distributions, with the help of Zeeman-Doppler imaging.