Good Quotes by Famous People - from Gabe Robins, University of Virginia - provides interesting and humorous quotations, but it is a list only with no subject/author guide or index.

Latin Quotations

Quotations Home Page "This [site] is one of the oldest and largest on the Web." It has useful indexes and guides to quotations (e.g., recent quotes, advice, great leaders, proverbs, sarcasm, lists by topic, lists by speaker, poems, wisdom, aphorisms, malapropism, and more).

The Quotations Page, established in 1994, contains over 15,000 quotations. It is searchable by author or keyword and has a subject index among other features, such as "Quote of the Day" and "Motivational Quotations."

Simpson's Contemporary Quotations provides over 10,000 quotations from more than 4,000 sources for the period 1950-1988. There is a search feature, or you can browse by source (author) or subject.

Toinspire.com provides a search feature by author or word. It includes 70 quotation categories, quotes to inspire, quotes of famous people, send a quote, etc.

Word Play - an excellent site for almost anything related to words. It links to numerous sites for abbreviations, acronyms, homonyms, slang, cliches, anagrams, multilingual dictionaries, and much more.