First of all, visit The Bernstein Experience. The website was unveiled after I put this list up, and it's TOTALLY worth your time!

This is everything I've researched so far on the genius Lenny. Each item gives a wider perspective on who he was, both as a person and professional, as well as his multitalents on teaching, composing and conducting. I find him exhilarating to watch, as it seems he felt the music in his veins and his soul. Some might think of him as an exhibitionist, whereas some are thrilled, to this day, with his visible passion for art, stamina on stage and sensitivity to modern interpretations of classical music in general. A remarkable figure in the history of American music.

I don't feel performance or composition recommendations would be relevant to this list, since a lot of his best moments are included in most documentaries, but I might list my favorite ones in a near future.

(I have yet to read or watch some of the listed items, check marks are on the ones I've watched):

• ✔ The Unanswered Question (at Harvard University, 1973, lectures)
  • I - Musical Phonology
  • II - Musical Syntax
  • III - Musical Semantics
  • IV - The Delights and Dangers of Ambiguity
  • V - The 20th Century Crisis
  • VI - The Poetry of Earth

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• ✔ Tanglewood (BBC and A&E, 1985, directed by Herbert Chapell, documentary)
  • So You Want To Be a Conductor?
  • A Place to Make Music

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• ✔ "The Rite of Spring" in Rehearsal (1987, documentary)
• ✔ Leonard Bernstein conducts "West Side Story" or The Making of "West Side Story": gives an insight into the recording of the West Side Story album, with singers José Carreras and Kiri Te Kanawa (1985, directed by Christopher Swann, documentary)
• ✔ Teachers and Teaching, an Autobiographic Essay (1988, directed by Humphrey Burton, documentary)
• Reflections (1978, directed by Peter Rosen, documentary)
• The Gift of Music (1993, directed by Horant H. Hohfeld, documentary)
• ✔ Reaching for the Note, from the American Music Masters series (PBS, 1998, directed by Susan Lacey, documentary)
• ✔ Inside Pop: The Rock Revolution, with David Oppenheim, Brian Wilson, Graham Nash, Frank Zappa and Janis Ian: Leonard narrates the first half of the documentary, commenting on pop music writing structures and themes (CBS, 1967, documentary)

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• Omnibus series (ABC, CBS and NBC, produced by the Ford Foundation, lectures)
  • ✔ Beethoven's Fifth Symphony (1954)
  • The World of Jazz (1955)
  • ✔ The Art of Conducting (1955)
  • American Musical Comedy (1956)
  • Introduction to Modern Music (1957)
  • The Music of Johann Sebastian Bach (1957)
  • What Makes Opera Grand? (1958)

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• Young People's Concerts series, (CBS, 1958-1972, educational TV programs)
  • According to Wikipedia, 53 episodes hosted by Bernstein were aired. The complete list is on the link above. I obviously haven't watched all of them, but I do have a few favorites:
    • ✔ What Is Classical Music? (1959)
    • ✔ Overtures and Preludes (1961)
    • ✔ What Is a Melody? (1962)
    • ✔ The Sound of an Orchestra (1965)
    • ✔ What Is a Mode? (1966)
    • ✔ The Anatomy of a Symphony Orchestra (1970)

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• An American Life, narrated by Susan Sarandon, featuring interviews with several musicians, as seen here (2004, produced by Steve Rowland, 11 hour audio-documentary)
  • whoever finds a link for it, I will thank you forever. I tried everything but couldn't find it to download or purchase - yup, I'm willing to spend money on this one. Actually, yhere is an eleven minute excerpt of the third part, but still.

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• Dinner With Lenny: The Last Long Interview (Jonathan Cott, USA, 2012, book)
• An American Musician (from Jewish Lives collection) (Allen Shawn, USA, 2014, book)
• ✔ Bernstein: A Biography (Joan Peyser, USA, 1998 [revised version], book)
• The Leonard Bernstein Letters, probably the most personal one, title is self-explanatory. The author himself gave a lecture on this book, at The Library of Congress, as seen here (Nigel Simeone, USA, 2013, book)
• ✔ Leonard Bernstein, (Humphrey Burton, Canada, 1994, book)

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• ✔ Manifestly Maestro (Howard Rosenman for LA Times Magazine, April 05 2009 issue, article)
• ✔ The Last Days of Leonard Bernstein (John Rockwell for The New York Times, October 16 1990 issue, article)
• ✔ Gustav Mahler rehearsals with Leonard Bernstein and the Wiener Philharmoniker, the 9th DVD of a box set released with LB's complete take on Mahler's symphonies, you can purchase it here (Deutsche Grammophon, Germany, 2005, dvd format)
• ✔ Bernstein - The Composer (Edward Seckerson for IDAGIO, 2018, playlist)
• ✔ Unearthed Footage of Leonard Bernstein's Last Rehearsals (Michael Cooper for The New York Times, 2018, video and article, also unveiling the Bernstein Experience, website completely devoted to Bernstein's centennial, as I first mentioned.)
• ✔ Lenny and me: memories of Bernstein (Humphrey Burton for The Guardian, September 17 2009, article)

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• The complete Beethoven's Symphonies, with additional commentary by the master himself (god bless whoever uploaded these to youtube, thank you forever)
  • (recordings with the Wiener Philharmoniker, between 1977 and 1981, I believe, and I have no idea where it was aired)
    • Symphony No. 1 in C major, Op. 21
    • Symphony No. 2 in D major, Op. 36
    • ✔ Symphony No. 3 in E-flat major, Op. 55 (Eroica)
    • Symphony No. 4 in B-flat major, Op. 60
    • ✔ Symphony No. 5 in C minor, Op. 67 (come on, y'all know this one)
    • Symphony No. 6 in F major, Op. 68 (Pastorale)
    • ✔ Symphony No. 7 in A major, Op. 92
    • Symphony No. 8 in F Major, Op. 93
    • Symphony No. 9 in D minor, Op. 125 (The Choral)