General

• Bartleby's Quotations - Via Bartleby.com, digital version of noted book; take advantage of the various options

• Quotation Archive - Great resource, from Aphids Communications; subject index particularly helpful

Specific Topics

• A Short Dictionary of Scientific Quotations - Alphabetical by author; with full citations

• Feminism - Quotegarden.com's lively section on feminism and women's liberation

• Shakespeare Quotes - From enotes.com; click on the beginning of the quote for the entire quotation with citation

• Buddhist Quotations - From rudyh.org; not searchable, but relatively abundant

• Quranic Wisdom -  From talkislam.com; very extensive

• Judaism Quotes - Brainyquote.com's section on Judaism

• Positive Atheism's Big List of Quotations - Use the menus on the left

• Rock Wisdom, Song Quotes - Quotations from over 13,000 songs; many search options

• Movie Sounds Central - Quotations in both print and audio formats

Quotes from Often-Quoted People

• Mark Twain - Site dedicated to Twain; hundreds of quotations organized by subject

• Albert Einstein - Ten pages worth, from Brainyquote.com

• Winston Churchill - Also from Brainyquote.com

• John F. Kennedy - Alphabetical by first word; searchable

• Malcolm X - From Malcolm-X.org