Other
Brunelleschi
This site provides the art of the well-known Florentine sculptor and architect, Brunelleschi. Each art clip is accompanied by a brief commentary describing the scene.
Other
Cupola: St. Peter's
On the oddly specific Cupola.com's page, you can scroll down to St. Peter's Basilica and find a few pictures of the dome.
Web Gallery of Art
Web Gallery of Art: Dome at St. Peter's
This site, which is provided for by the Web Gallery of Art, gives a brief description of the dome at St. Peter's as well as providing a picture.