The Parmenides is among the most enigmatic of Plato's dialogues, bringing Socrates into a profound metaphysical debate with two of the most influential Presocratic philosophers, Parmenides himself, and Zeno of Elea. The work fascinated ancient neoplatonist commentators, whose own interpretation of Plato emphasised his affinities with the Eleatic school.
Free Online and Downloadable Texts
Gutenberg: Parmenides by Plato, translated by Benjamin Jowett, multiple formats.
Internet Classics Archive: Parmenides, translated by Benjamin Jowett. Online text.
University of Adelaide (Internet Archive): Parmenides, translated by Benjamin Jowett. EPUB, HTML and MOBI formats.
History of Philosophy without any gaps: Second Thoughts: Plato's Parmenides and the Forms - podcast by philosopher Peter Adamson.
Librivox: Parmenides - audiobook.
Ontology.co: Plato's Parmenides and the Dilemma of Participation.
PhilPapers: Plato - Parmenides - bibliography with open source option.
Stanford Encyclopedia of Philosophy: Plato's Parmenides.
YouTube: History of Ancient Philosophy - Plato's Parmenides. Lecture by Adam Rosenfeld.
The Great Conversation: Further reading at Tom's Learning Notes
Ancient Greek resources: Learn to read Greek classics in the original.
Bloom's Western Canon: Plato's Dialogues are listed.