Herodotus: Solon and Chroesus: Link
Plato: Republic, II, 357 A-368 A; IV, 336 A-445 E; IX, 571 A-592 B: Link
(Go to Greek and Roman materials). Also in Curd, Cohen and Reeve (CCR)
Aristotle, Nicomachean Ethics, books I. and X. Available at: Link
Also in CCR.
Epicurus and Epicureans: Letter to Menoeceus, Principal Doctrines, Vatican sayings, Cicero:
About the Ends of Goods and Evils, Book I (De Finibus, Bonorum et Malorum, Liber Primus), Lucretius: On the Nature of Things
(De Rerum Natura) III. 800ff. All at: Link
Stoics and Plotinus: Cicero: On Ends book III (De finibus bonorum et malorum) at: Link
Epictetus: Enchiridion (Handbook) http://classics.mit.edu/Epictetus/epicench.html
Seneca, Letter 32: Link
Plotinus. Ennead I.5 Link (1st Ennead, 2nd tractate).