And don't start with the Wagner.
Yeah, if I listed them in order of accessibility (and thus, the order you should listen to them if you're totally new to opera), it'd go Carmen, Rigoletto, Turandot, Nozze di Figaro, De Frau ohne Schatten, Tristan.
--M.
And to add a few more (non-opera) I thought of while I was in the shower:
Ella Fitzgerald: The Cole Porter Songbook, vols. 1 and 2
Duke Ellington: Black, Brown, and Beige
Fleetwood Mac: Rumours
The Nitty Gritty Dirt Band: Will the Circle Be Unbroken (the first one, not either of the two sequels)
Janis Joplin: Pearl
Metallica: Metallica (the "black album")
--M.

Brubeck -- Take Five
Blondie -- Parallel Lines
Talking Heads -- Stop Making Sense
Police -- Synchronicity
Donald Fagen -- The Nightfly

Here we go again:
-Coyote Oldman 'Landscapes'
-Nigel Kennedy 'East Meets East'
-Ween 'Quebec'
-Geoffrey Oryema 'Beat the Border'
-Abdelli 'New Moon'
-Cesaria Evora 'Cesaria'
-Neil Young 'Harvest'
-Bob Dylan 'Blood on the Tracks'
-Tea Party 'Edge of Twilight'
-The Tubes debut
-Beleza Tropical as compiled by David Byrne
-Eno 'Music for Airports'
-Radio Tarifa 'Rumba Argelina'
-Zappa 'One Size Fits All'
-Gentle Giant 'Free Hand'
-Max Webster 'High Class in Borrowed Shoes'
-Gorecki's 3rd
-Lhasa 'La Lloronha'
-Grand funk 'Closer to Home'
-UFO live album
-Mickey Hart 'Planet Drum
-Bruce Cockburn 'Dancing in the Dragon's Jaw'
-Natasha Atlas; Wasis Diop; Rachid Taha (any album)
-Montrose debut; ELP (same)
-David Gilmour solo (1977)
-Steely Dan's Greatest Hits
-Uriah Heep 'Sweet Freedom'
-Bowie 'Low'
-Zebec live Young Station New Years Eve '78
-Bad Company debut
-Stones 'Exile on Main street'
-Hendrix-everything
-The Doors hits; Cream, Janis Joplin, Cat Stevens, Heart (same)
-Police 'Reggatta de Blanc'

Fleetwood Mac -- Rumours
Bee Gees -- Saturday Night Fever Soundtrack
ABBA -- sorry, but "Gold" is a "best of" album, but it's really the best of, and the only one that matters
Beethoven -- Fifth Symphony. Great piece for driving, played very loud. :oD Not that I do that.
REM -- Eponymous

Cyndi Lauper -- She's So Unusual
Squeeze -- 45's and Under
Hedwig and the Angry Inch (Soundtrack. I suggest watching the movie, to make the songs make more sense, much like Pink Floyd's The Wall)
Devo -- Oh No It's Devo, or New Traditionalists (New Wave/synth at it's cynical best)
B-52's -- Cosmic Thing (Just when everyone thought they went away, this album EXPLODED)
Beat/English Beat -- Special Beat Service
That should get you started. I will shut up now. :oD

Forgot:
-Beirut 'Flying Club Cup'
-Radiohead 'In Rainbows'
-Jeff Buckley debut
-Oasis 'What's the story...'
-Joni Mitchell 'Court and Spark'
-Talvin Singh 'Traveller'
-Rick Tyrell 'Art Carcass'
-Alice Cooper 'Billion Dollar Babies'
-Rush 'Moving Pictures'
-Floyd 'Wish you were here'
-Gary Numan 'Replicas'
-Simon + Garfunkel 'Bridge over troubled water'
-George Harrison 'All Things Must Pass'
-McCartney "Band on the run'
-Andreas Vollenweider 'Caverna Magica'
-Jon Hassel 'Possible Musics'
-Africa Never Stand Still--anthology
-Baaba Maal 'D'jam Leeli'
-Strawbs "Hero and Heroine'
-Genesis 'The Lamb'
-Jethro Tull 'Aqualung'
-Elton John 'Honky Chateau'
-Sly and the Family Stone Greatest Hits
-Zep 4
-Yes 'Close to the Edge'
-Deep Purple 'Machine Head'
-Black Sabbath 'Sabatoge'
-Robin Trower 'Bridge of Sighs'
-Beach Boys 'Holland'
-Stevie Wonder Best Of
-Supertramp 'Breakfast in America'
-Styx 'Grand Illusion'
-Foreigner debut
-Kansas 'Leftoverture'
-Billy Joel Best of
* I am done. The End.

I am not done: the Best of the following are excellent.
The Guess Who; Queen; Gordon Lightfoot

Where do I start? 1001 is about half of my CD collection. I'll suggest some composers, but if I list all the works I'd recommend I'll be here all day. In roughly chronological order;
Guillaume de Machaut
Guillaume Dufay
Josquin Des Préz
John Taverner (not to be confused with John Tavener)
Roland de Lassus (otherwise known as Orlando di Lasso)
William Byrd
Giovanni Gabrieli
Carlo Gesualdo (Tenebrae Responsories for Holy Saturday in particular)
Henry Purcell
Antonio Vivaldi
Johann Sebastian Bach (obviously)
Wolfgang Amadeus Mozart (obviously)
Ludwig van Beethoven (obviously)
Franz Schubert
Hector Berlioz
Felix Mendelssohn
Robert Schumann
Anton Bruckner
Piotr Ilyich Tchaikovsky
Antonín Dvořák
Edvard Grieg
Charles Hubert H Parry
Leoš Janáček
Edward Elgar
Isaac Albeniz
Gustav Mahler (go for the symphonies)
Frederick Delius
Claude Debussy
Richard Strauss
Carl Nielsen
Jean Sibelius
Alexander Scriabin
Ralph Vaughan Williams
Sergei Rachmaninov
Josef Suk
Gustav Holst
Maurice Ravel
Manuel de Falla
Ottorino Respighi
Béla Bartók
George Enescu
Igor Stravinsky
Zóltan Kodály
Sir Arnold Bax
Alban Berg
Heitor Villa-Lôbos
Bohuslav Martinů
Sergei Prokofiev
Darius Milhaud
EJ Moeran
Paul Hindemith
George Gershwin
Francis Poulenc
Kurt Weill
Aaron Copland
William Walton
Aram Il'yich Khachaturian
Dmitri Shostakovich
Olivier Messiaen
Witold Lutoslavski
Benjamin Britten
Leonard Bernstein
Malcolm Arnold
Arvo Part
That's far from a comprehensive list, just some of my favourites...