An important problem in pervasive computing is how to create and maintain manageable collections of pervasive resources appropriate for disparate and typically nomadic users. This paper describes physical registration, a new, human-centric mechanism for constructing collections of resources in the form of electronic directories. Users identify physical objects using sensor-equipped, wirelessly networked handheld devices to build directories of virtual "entities" associated with those objects. The entities can be web resources accessible over a network, like printers, projectors, picture frames, or storage devices. They can also be web resources correlated with objects like books or telephones that are not themselves accessible over a network. Our paper describes and motivates the method, then compares two implementations that we have constructed. 13 Pages