April 29 is the feast day of St. Catherine of Siena.
Catholic Forum bio by Edmund G. Gardner
Dominicans website by Mary Ann Sullivan
Sisters of St. Dominic of Amityville, New York by Laura M. Arvin, O.P.
The Dominicans have her Letters online in English.
Christian Classics Ethereal Library has her Dialogue as translated by Algar Thorold.
Artwork about her:
Stained glass windows at the Cathedral of Milano (Shown here is the window depicting St. Catherine of Siena as she goes to Pisa where religious men and laics are waiting for her. Photo credit: Laura Monciardini)