...here are some of my favourites, and no drum solos here:

Genesis- Supper's Ready, The Cinema Show, Firth Of Fifth, The Musical Box, The Knife
Yes- Awaken, Close To The Edge, The Gates Of Delirium
Rush- Xanadu
Rainbow- Stargazer
Uriah Heep- July Morning, Paradise/The Spell
Marillion- The Invisible Man, Neverland, This Strange Engine
Van Der Graaf Generator- Plague Of Lighthouse Keepers, Lost
Led Zeppelin- Kashmir, In The Light, No Quarter (love the live version of this on 'The Song Remains The Same' in particular), Achilles' Last Stand
Nektar- A Tab In The Ocean
Man- C'Mon (live version on 'Back Into The Future' with Welsh male voice choir no less, and it's brilliant)
Barclay James Harvest- She Said
Fairport Convention- A Sailor's Life, Sloth
Bruce Springsteen- Jungleland
Van Morrison- Summertime In England, When Heart Is Open, Listen To The Lion, Almost Independence Day
Deep Purple- Child In Time
Isaac Hayes- Walk On By, By The Time I Get To Phoenix
David Bowie- Station To Station, Sweet Thing/Candidate/Sweet Thing, The Width Of A Circle
Jethro Tull- Thick As A Brick Part 1
Neil Young- Like A Hurricane
The Who- Won't Get Fooled Again

I used to be the same, if a track on an album was over 5 and a half minutes I just presumed it was flabby twaddle. The song that changed my mind was Gillian Welch's I Dream a Highway on Time (the Revelator). A song of David Lean like proportions, at 14 minutes and 46 seconds. But when it finishes I always contemplate putting it on again. I'm pretty sure Wire's Pink Flag LP isn't much longer, and there is 20 odd songs on that.

Pink Floyd- Echoes
Funkadelic- Maggot Brain
Al Stewart- Nostradamus

Is the longest UK number one single still Laurie Anderson's "Oh Superman?"

Primal Scream have never released a single called "Screamadelica".

They did release Come Together which is over 10mins long on the album but the single release was a few minutes shorter (and better).

Eastern Mantra - Cabaret Voltaire (20.39)
Smokebelch II (David Holmes remix)(14.26) The Sabres of Paradise
Terminus - Xtul - Psychic TV (13.20)
The Perfect Kiss - New Order (8.02)
And This Day - The Fall (10.18)
Parents - Budgie (10.12)

Definitely seeking to be pedantic (why am I here otherwise...?) here but Primal Scream DID, in fact, release a track called 'Screamadelica' on a single they called the Dixie Narco EP - it has 4 tracks and Sreamadelica took up one side of the 12" EP (I LOVED 12" singles...so much more than 7"...!!)

On other long songs, Neil Young is the master, Crime in the City (the original from 1989, before it was edited for the freedom LP) was about 12-15 mins long and Ordinary People - unreleased and legendary until last year's Chrome Dreams II CD - usually about 20-25 mins long.

At his recent European concerts, Neil was clocking an average of 20 mins for the performance of 'No Hidden Path' from that CD, and (fact fans) the view amongst the cognescenti is that the tour he has just completed saw him perform some of the SHORTEST ever versions of 'Like A Hurricane' - named elsewhere in this parish as a looooooooong song...and yes, my wife knew I was like this before she agreed to marry me...!!

....and did someone mention 'Desolation

A master of the long song. The quality varies from the excellent:
One Of Those Days In England (parts 2 - 10)
The Game (parts 1 - 6)
The Lord's Prayer
the 4 songs on Stormcock
Work of heart (parts 1 - 6)

to the middling:
McGoohan's blues

to the poor:
Burn The World

and there are more. I haven't included Old Cricketer as it's only about 8 minutes long.

Finally bought Neil Young's Chrome Dreams 11 yesterday for £6.99, what a bargain. Go to Relics in Leeds for more bargains, great vinyl section downstairs too.
Anyway, already enjoying the epic 18 mins and 13 seconds of Ordinary People. Great stuff. Long is sometimes good too.

A sweep through my itunes reveals this clutch of over-ten-minuters:

Spiritualized - Cop Shoot Cop (16:17); Wont Get To Heaven (The State I'm In) (10:33)
Nick Cave - Babe I'm On Fire (14:46) ; O'Malley's Bar (14:28)
Flowered Up - Weekender (12:56)
The Doors - The End (11:40)
Morrissey - The Teachers Are Afraid Of The Pupils (11:20)
Jamiroquai - Revolution 1993 (10:17)
Guns 'n' Roses - Coma (10:14)
Daft Punk - Too Long (10:00)

Steely Dan - Aja (8:00)
Dylan - Hurricane (8:33), Lily, Rosemary and the Jack of Hearts (8:52)
VU - White Light/White Heat (8:38)
Was Not Was - (Return To The Valley Of) Out Come The Freaks (8:39)
Van Morrison - You Don't Pull No Punches, But You Don't Push The River (8:50)
Kraftwerk - Autobarn (8:52)
Suicide - Frankie Teardrop (10:26)
Television - Marquee Moon (10:40)
Dexys - This Is What She's Like (12:19)
Panda Bear - Bros (12:30)
Shuggie Otis - Feedom Flight (12:58)
Gruff Rhys - Skylon! (14:36)
Can - Aumgn (17:34)
godspeed you! black emperor - East Hastings (17:58) (anything by them in fact!)

...Iron Maiden - Rime Of The Ancient Mariner (13.34)

Canned Heat: Refried Boogie (41 minutes). Used to have to turn over the record halfway through. God, it was terrible.

Someone mentioned Echoes at 23 mins but what about Dogs (17 mins), Shine On You Crazy Diamond Part 1 (15?) and Part 2 (13?). And Pigs (Three Different Ones) (11).

And:

The Gathering - How To Measure A Planet? (28 mins instrumental)

Mike Oldfield - Tubular Bells Parts 1 and 2 are 25 mins each.

Van Der Graaf Generator - A Plague Of Lighthouse Keepers (23)

Tarkus by ELP (20) and Piartes (13).

The End by The Doors (11).

And various tracks by Tool.

VU - Sister Ray (17:00. Great riff, battle between organ and guitar!
Television - Little Johnny Jewel from Blow Up (live)album. Tom Verlaine at his mesmerising best.
Can - Chain Reaction (11:09), Mother Sky (14:31), Hallewulah (18:32). Hypnotic and ahead of it's time.
Neil Young - Down By the River (9:13), Cowgirl in the Sand (10:06), Ambulance Blues (8:57). Sustains interest - compelling.
Soft Machine - Facelift (18:45) plus three other tracks each take up one side of double album. The best Soft Machine album?
Talking Heads - Born Under Punches (The Heat Goes On) (8:24) from The Name of this Band is Talking Heads (live). Some of the best Talking Heads performances on this album and features great guitar from Adrian Belew.

"Chillout" by KLF is just under 45 minutes long
"Mountain Jam" by the Allmans just under 34 minutes
"Pyramidflutenik" by Nik Turner's Sphynx (ulp)is 29.51

Giving far too much of myself away here !!!

By Arlo Guthrie clocks in at 18:32. Not the 25 minutes he claims in the lyrics. His remake "The Massacree Revisited" is even longer.

I think it's called "Screamadelica". From the "Screamadelica" ep. but it didn't appear on the album called "Screamadelica".

by Brian Eno is about 63 minutes long, I believe

Voodoo Chile (album version) - Jimi Hendrix 15.00
Rappers Delight - Sugarhill Gang 14.36
Madame George - Van Morrison 9.45
November Rain - Guns n Roses 8.57
Pain in Any Language - Billy MacKenzie 8.40
Sheffied, Sex City - Pulp 8.32
I Am the Resurrection - Stone Roses 8.14
My Sister - Tindersticks 8.11

...takes the biscuit for longest track of all time. It started on 1 January 2000 and will finish on 31 December 2999. Then it will start all over again. Details and a link to a live internet stream are here.

On their excellent DISINTEGRATION there are "The Same Deep Water As You" 9:22, and "Disintegration" 8:23. There's also "Pictures Of You" that lasts 7:28.

When they play live, "A Forest" and "Faith" oftentimes last(ed) 10+ minutes.

The most recent album, Ys, features only 5 tracks which clock in at respectively:
Emily 12m 09s
Monkey & Bear 9m 29s
Sawdust & Diamonds 9m 56s
Only Skin 16m 53s
Cosmia 7m 17s

and each one a masterpiece in their own right!

Next we'll be 'dondle'ing or something.

'Lately' by the excellent British Sea Power is a good one, as is the second track off 'The Crane Wife' by The Decemberists. Forget what it's called.

Bob Dylan´s Highlands from Time Out of Mind is only 16 minutes and 30 odd seconds long but somehow it seems even longer.

Seek out any Acid Mothers CD - most songs range from 45-60mins - no need to recommend/suggest any particular one - every track is awesome (...after ingesting some heavy psychedelics!)

Philip Glass - Music With Changing Parts (61:35)
Goldie - Mother (60:05)
The Orb - Blue Room (39:37)
Miles Davis - He Loved Him Madly (32:10)
Sonic Youth - Four6 (29:46)
Miles Davis - Bitches Brew (26:57)
Mike Oldfield - Tubular Bells Part One (25:28)
Jon And Vangelis - Horizon (22:40)
Kraftwerk - Autobahn (22:33)
Yes - Ritual/Nous Sommes Du Soleil (21:49)
Prince And The Revolution - America (21:40)
New Order - Video 5 8 6 (21:40)
Goldie - Timeless/I. Inner City Life/II. Jah/III. Pressure (20:57)
The Orb - A Huge Ever Growing Pulsating Brain That Rules From The Centre Of The Ultraworld (Loving You) (20:09)

If it isn't over 20 minutes, the artists concerned just aren't trying hard enough. Or perhaps the reverse.

And having listed all that, my favourite really long track is Dexy's Midnight Runners' This Is What She's Like which clocks in at a relatively sedate 12:17.

Remember back in the seventies when soul groups such as The Temptations and Harold Melvin & The Blue Notes would string out a song by having Part 1 on the A side, Part 2 on the B side and the whole caboodle on the album? Try Papap Was A rolling Stone for starters.

no one else will admit a liking for this, but old habits die hard and as the stand out track from one of the first albums I bought (`Once Again` for 7p from Naomi Harris`s jumble sale in 1983) `She Said` by Barclay James Harvest is a long `un (8:12)and though it could be edited to a four minuter without anyone grumbling, it is a much loved indulgence.

Sao Paulo by The Guillemots is a great way to spend 11:38. I remember Phill Jupitus playing it in its entirety on the 6 music breakfast show.
iTunes suggests anything by Godspeed You Black Emperor! is over 15 minutes.
Rappers Delight was a good 12 minutes I recall.
The Crown by Gary Byrd was even longer I recall - and did it get to number 1?

Can I add Porcupine Tree's 'Anesthetize' (17:42) off of 'Fear Of A Blank Planet' to the list...and just declare that they are finally coming down to Australia next month (pause for applause)and I was also going to add Jim O'Rourke's 'Women Of The World' from his 'Eureka' album but whilst I've always thought it exceeded 10 minutes, I have just put it in my computer to find it only clocks in at only 8 mins 46 secs...another long held belief shattered!

There is a Four Tops song which is 10 mins +. Can't remember the name of the top of my head. Not someone you would associate with 10 minute epics!

Recorded a fine track (well, I liked it) called The Ikon on the Todd Rundgren's Utopia LP which clocked up 30 minutes 22 seconds and was crammed into Side 2 of the LP. Is this a record?

with 'Smiling Faces Sometimes'... clocking in at 12.06.