That's a hard one, in that there are so many, and it is very objective. However, here's thirty or so that always bring me joy and I wouldn't change a note on from my rock/folk world to start.
Disraeli Gears & Wheels of Fire
Are You Experienced
Crosby, Stills & Nash
Sgt Pepper, Rubber Soul
Their Satanic Majesties Request
High Tide and Green Grass
Abraxas
Sunshine Superman
Saucerful of Secrets, Meddle, Wish You Were Here
Oranges and Lemons
Liege and Lief
S.F. Sorrow
Odessey and Oracle
Grave New World
Close to the Edge
Selling England by the Pound
Bundles (Soft Machine)
Bryter Later (or any Nick Drake)
Strange Days
Surrealistic Pillow, Crown of Creation
Electric Music for ther Mind and Body (Country Joe and the Fish)
The Grateful Dead (first album)
Fifth Dimension (The Byrds)
Psonic Psunspot & 25 O'clock (Dukes of Stratosphear)
Chicago Transit Authority
Allman Brothers Live at the Filllmore East
Blue, Miles of Aisles, Don Juan's Reckless Daughter (Joni Mitchell)
and finally one most of you will never have heard of, but is well worth picking up on vinyl if you can find it: Viva Tirado by 70s Latin Soul band El Chicano. (Think Santana with Wes Mongomery style guitar.)
El Chicano doing Herbie Hancock's "Cantaloupe Island":
http://www.youtube.com/watch?v=SsxFVCws760 Enjoy.
Have to agree on Who's Next and the Zeps. I know I'll think of another hundred in a few minutes. It's interesting to me how many come from the late 60s and the 70s, but that's also the era of maximum emotional resonance for me.