The University of Michigan, along with the following institutions, is a member of a consortium of American universities intending to bring their papyrus collections online with a project called APIS, the Advanced Papyrological Information System. The databases being compiled at each university contain detailed information on each inventoried papyrus in the various collections.
The Michigan APIS database currently has over 3500 records with images, searchable in a variety of fields including date, language, origin, type of text, author, names of persons, and many more. Also included are detailed electronic images of the papyrus, publication info, and even (in some cases) a link to the Greek text on the Perseus website.
A brief article about APIS by Traianos Gagos was printed in the Classical Studies Newsletter and can be read here.
You can search all Michigan Papyri from the U-M APIS Homepage.
Below are links to other universities participating in the APIS project.
The Tebtunis Papyri Collection and the Advanced Papyrological Information System at The Bancroft Library consist of the papyrus documents that were found in the winter of 1899/1900 at the site of ancient Tebtunis, Egypt. Although the collection has never been counted and inventoried completely, the number of fragments contained in it exceeds 21,000. This web site, which is still under development will eventually provide electronic access to the images of the Tebtunis Papyri along with textual information.
The Columbia University APIS page contains a searchable database of the papyri in their collection and provides detailed information on the individual pieces, although not many images have yet been added. Also available at this site are links to the other APIS institutions, as well as bibliographies having to do with papyrological study.
The Duke Papyrus Homepage provides electronic access to texts about and images of 1,373 papyri from ancient Egypt. The databank is useful for papyrologists, ancient historians, archaeologists, biblical scholars, classicists, Coptologists, Egyptologists, students of literature and religion and all others interested in ancient Egypt. Click here to search the Duke Papyrus Archive. The Duke Papyrus Homepages also contain information on the Duke Databank of Documentary Papyri, which is available online through the Papyri.info.
Princeton's APIS page makes available a descriptive inventory of the papyri housed in the Manuscripts Division of the Department of Rare Books and Special Collections in the Harvey S. Firestone Memorial Library, along with images of several papyri.
The Beinecke Library at present provides a searchable on-line catalog of the papyri of the Rare Book and Manuscript Library. Information on the collection and on searching the catalog is available here.