"A well-chosen quote can strengthen a speech by emphasizing and reinforcing a point, tapping into the audience's memories and associations, and bolstering the speaker's credibility. The right quote can capture the listener's attention, add poignancy, and infuse drama or poetic flair. The following resources will help the user find quotes for speeches and other communications. The resources are divided into three categories: (1) General Quotations, (2) Americana, and (3) Religion. There is some overlap among the categories."
CRS Report for Congress, R44200
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html