We present the design and initial evaluation of TerraDir: an approach for implementing customizable, distributed, peer-to-peer directories over which a broad range of wide-area resource discovery applications can be implemented. TerraDir's structure is two-tiered, consisting of a base protocol for providing arbitrary application-layer connectivity, and dynamic view materializations that efficiently realize different user-specified views of application-layer resources. TerraDir is specifically designed for data that can be arranged in a rooted hierarchy, and provides very efficient and robust lookups over such data while still being able to allow efficient searching. (Also referenced as UMIACS-TR-2001-4299)