Collège de France Library - extensive holdings for Buddhism and other Asian religions with holdings including Institut d'Etudes Tibétaines, Institut d'Etudes Indiennes, Institut d'Etudes Coréennes, Institut des Hautes Etudes Chinoises and Institut d'Etudes Japonaises. Indexes books, articles and theses.
Dhagpo Kagyu Library - This library specializes in Buddhism and in Tibetan civilization and holds approximately 3,000 works.
University of Virginia Library - holds a large collection of Tibetan texts and secondary material. Can search the library catalog to identify books titles and some journal articles. While you can filter results by language, the list of languages is arranged by number of hits so it can be challenging to quickly find Tibetan.