On the Ends of Good and Evil or On Moral Ends (Latin: De finibus bonorum et malorum), composed by Cicero in 45 BC, presents the ethical teachings of the major philosophical schools of the time in the form of dialogues recounted by Cicero to his friend Brutus. Lucius Torquatus serves as spokesman for epicureanism in the first two books, while Cato represents stoicism in books three and four. Book five presents Cicero's own academic skepticism.
Free online texts
Gutenberg: The Academic Questions, Treatise De Finibus, and Tusculan Disputations. Multiple formats.
LacusCurtius: de Finibus, translated by H. Harris Rackham. HTML format.
Latin Library: De Finibus Bonorum et Malorum. Latin text, HTML format.
Perseus: De finibus bonorum et malorum (Teubner, 1915). Latin text, HTML and XML format.
University of Adelaide (Internet Archive): Treatise de Finibus, translated by Charles Duke Yonge. Multiple formats.
Wikisource: De finibus bonorum et malorum. Latin text, multiple formats.
History of Philosophy without any gaps: Rhetorical Questions: Cicero - podcast by philosopher Peter Adamson.
History of Philosophy without any gaps: Raphael Woolf on Cicero - podcast by philosopher Peter Adamson.
Internet Encyclopedia of Philosophy: Cicero.
Librivox: On the Ends of Good and Evil - public domain audiobook.
The Obstinate Classicist: On Moral Ends, summary by Bill Prueter.
The Great Conversation: Further reading at Tom's Learning Notes
Cicero: Academica - dialogue on stoic and academic views of the theory of knowledge.
Cicero: Tusculan Disputations.
Plato: Phaedrus - cited by Cicero in Book Two.
Latin resources: Learn to read Latin texts in the original.