The nature of the neutral, monatomic states of interstitial hydrogen in a wide range of oxides, both semiconducting and dielectric, has been surveyed experimentally via μSR spectroscopy of their muonium counterparts. The states fall into three categories: shallow donor, deep donor and trapped atom — these latter probably the neutral state of deep acceptors. New examples are found in all three categories, giving an emerging picture of the systematics, for comparison with current theoretical models of the electrical activity of hydrogen impurity.