As a fan of side long songs (as they were called in the vinyl days), I have attempted to create a list of the ones I am aware of (the word intro tells how long it takes until the vocals start):
68 IAGDV – Iron Butterfly (intro :25)
69 Eight Miles High - Golden Earring (Intro :47)
70 Atom Heart Mother – Pink Floyd (Instrumental)
71 Echoes -PF (Intro 2:58)
71 Salisbury – Uriah Heep (intro 3:12)
72 Thick as a Brick, Part 1 – Jethro Tull (intro :10)
72 Thick as a Brick, Part 2 – Jethro Tull (intro :54)
72 Supper’s Ready – Genesis (intro :01)
72 Close to The Edge - Yes (intro 4:02)
73 Tales from Topographic Oceans -Yes (intro 1. 1:37(cd version); 2. :38; 3. 4:16; 4. 5:28)
73 Karn E9 – EL&P (intro :25)
74 Gates of Delirium – Yes (intro 2:11)
75 Shine on You Crazy Diamond – PF (intro 8:42)
75 Fountain of Lamneth – Rush (intro :22)
76 2112 – Rush (intro 4:25)
77 Dogs – PF (intro :37)
78 Hemispheres – Rush (intro 2:59)
81 As Falls Wichita, So Falls Wichita Falls – Pat Metheny & Lyle Mays (instrumental)
88 Ivory Gate of Dreams – Fates Warning (intro 2:08)
92 Achilles, Agony and Ecstasy in Eight Parts – Manowar (intro 1:31)
95 Change of Seasons – Dream Theater (intro 4:15)
95 Dante’s Inferno – Iced Earth (intro :16)
96 That, That Is – Yes (intro 4:44)
97 Mind Drive – Yes (intro 3:59)
05 Fullness of Time – Redemption (intro 1:12)
08 Octavarium – Dream Theater (intro 5:33)
09 Count of Tuscany – Dream Theater (intro 4:24)
13 Illumination Theory – Dream Theater (intro 3:57)
13 From the Ages – Earthless (instrumental)
15 Empire of the Clouds – Iron Maiden (intro 2:06)
15 Greatest Show on Earth – Nightwish (intro 3:46)
15 Ash Memory – Wilderun (intro 2:03)
I almost included A Nightmare to Remember by Dream Theater but at 16 minutes long, thought it might be just shy of an lp side.
Let me know of any I missed!