Modern Hagiography
Lives of the Saints by Sabine Baring-Gould.
Medieval Hagiography
The Cult of Saints in Late Antiquity Database
Gregory the Great, Dialogues (also here)
Art & Architecture
Warburg Institute Iconographic Database
Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.
Nihil sub sole novum 