Saint Jerome on the Web -
Angel Appearing to Saint Jerome
Very large, clear image of the painting by Guido Reni includes informative text. (This site is no longer live; the above link is made available through the Internet Archive.)
Life, Death and Miracles of Saint Jerome
A collection of images from the late 15th- or early 16th-century French book includes photos of the binding, large jpegs of pages, and a complete set of vivid miniatures.
The Penitent Saint Jerome
Large image of the oil-on-panel by Lorenzo Lotto.
Large, excellent scan of the piece by Giotto at Carol Gerten's Fine Art Museum.
Painting by Marinus Claeszon van Reymerswaele (c.1490-1567) links to larger version and is accompanied by background info. (This site is no longer live; the above link is made available through the Internet Archive.)
Seventeenth century work by Guido Reni; click the small image to see a larger version.
Saint Jerome in the Wilderness
Large image of Albrecht Durer's work at CGFA .