From this source, on NT textual criticism, itself well worth reading, I learn of two databases which are worth a look.
The Pinakes database (http://pinakes.irht.cnrs.fr/) aims to bring together catalogue entries for all manuscripts of Greek texts predating the sixteenth century, supplementing the
Leuven Database of Ancient Books (LDAB, http://www.trismegistos.org/ldab/).
The latter gave some interesting results. Who would have imagined that we have a 4th century fragment of the Church History of Eusebius?