Biography Online includes the section Spiritual Biographies covering prominent spiritual leaders.
Christian Biography Resources, from Wholesome Words, provides brief biographical sketches of a selection of prominent Christians.
The Biography section of the Jewish Virtual Library provides biographical information on Jewish Women, Rabbis & Religious Figures, Jewish Fashion Icons, Jewish Nobel Prize Winners, Jewish Recipients of the Congressional Medal of Honor, and Jews in Sports. It also includes a Bibliography of Autobiography & Biography.
From the Adherents.com web site, Famous Adherents provides links and biographical information on famous people of various religious persuasions.