Aristotle’s works, of which there are very many, are available in the Greek-English Loeb edition:
Browse In Aristotle | loeb | Loeb Classical Library
Perseus Digital Library contains Greek and English versions of Aristotle’s works: Athenian Constitution, Economics, Eudemian Ethics, Metaphysics, Nicomachean Ethics, Poetics, Politics, Rhetoric, and Virtues and Vices.
Project Gutenberg – Online Book Catalog
Project Gutenberg is an online book catalogue which allows browsing by author (alphabetically), title, language, categories, or recently added and searching by author or title. This website is the first and largest single collection of free electronic books. Project Gutenberg has Aristotle’s works in Greek and English.