This may be the best place to start looking for information about Florence's history, art and buildings. Firenze, Toscana A good overview of history, important monuments and people for Florence and the region. Florence, Italy Clear writing, by Jacob Avidon, about important events in Renaissance Florence.
Links provide earlier and later history.
Renaissance Art Mary Ann Sullivan at Bluffton College has created an important database of useful images with good commentary. Renaissance Architecture Many good slides, mostly of Brunelleschi's work, from the University of Virginia's School of Architecture. This is an impressive set of images, made by Patrick Young, for the University of Michigan. Sandro Botticelli Painting, commentary and history from the WebMuseum, Paris. The Galileo Project Timelines and other useful information about Galileo.