The Lysis (Greek: Λύσις) is a dialogue by Plato on the nature of love and friendship.
Free Online Texts
Gutenberg: Lysis by Plato, translated by Benjamin Jowett, multiple formats.
University of Adelaide (Internet Archive): Lysis, translated by Benjamin Jowett. EPUB, HTML and MOBI formats.
Wikisource: Lysis, translated by Benjamin Jowett, online text.
Approaching Plato: A Guide to the Early and Middle Dialogues
History of Philosophy without any gaps: Wings of Desire: Plato's Erotic Dialogues - podcast by philosopher Peter Adamson.
Librivox: Lysis - audiobook
Philpapers: Plato - Lysis - open access papers.
Stanford Encyclopedia of Philosophy: Plato on Friendship and Eros, by C.D.C Reeve.
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.