The atomic gas (HI) content of nearby galaxies provides important insight into how they form and evolve within the standard cosmology. In this talk, I will highlight some of my group’s recent progress towards building statistical samples of HI detections for nearby galaxies to use as cosmological probes. I will first focus on how sensitive HI follow-up observations of optically-selected dwarf and ultra-diffuse galaxy candidates are a powerful tool for measuring their structure and constraining formation models. I will then describe how the WALLABY survey, now underway on the Australian SKA Pathfinder (ASKAP) telescope, is delivering the first spatially-resolved populations of HI disks for comparison with cosmological predictions. I will finish by explaining how this work paves the way for probing HI in galaxies widely and more deeply than ever before with a new generation of radio facilities that are under construction now, including the billion-dollar SKA telescope in which Canada will soon become a full member.