Can be any type of rock or metal as long as there are lots of changes and lots of ideas. Can range from 5 minutes to an hour (no longer than that, and yes I have heard of Bull of Heaven). No drone please, I already have tons of it, and varied it is not! Ones I already know that I would like to share:

The Gathering (yes Im a little obsessed with them):
http://www.youtube.com/watch?v=ggju71o0lmE - Sand and Mercury
http://www.youtube.com/watchv=0zS9XE02U ... 1&index=85 - Black Light District Part 1
http://www.youtube.com/watch?v=SxZ331ot ... re=related - Black Light District Part 2
http://www.youtube.com/watch?v=oNYg2iTEhmA - Travel
http://www.youtube.com/watch?v=lT2yKYUDjk4 - How to measure a planet part 1
http://www.youtube.com/watch?v=kkV0tYRx ... re=related - How To measure a planet part 2
http://www.youtube.com/watch?v=qdxOCV23 ... re=related - How to measure a planet part 3

Porcupine Tree - anesthetize (cant find a link)

Led Zepelin - stairway to heaven and Queen - Bohemian Rhapsody shouldnt require a link, neither should GNR - November Rain (not really THAT varied but its kind of a guilty listen for me)

Wyrd -
http://www.youtube.com/watch?v=pvBd0INLIrM - sad song of the woods part 1
http://www.youtube.com/watch?v=mW676Fg_ ... re=related - sad song of the woods part 2

Also Heathen by Wyrd, but at 51 minutes long I think 6 links would be a bit much

I know more, but anyway this is the sort of thing I mean with most of them, but can be any style

Satan's fall by Mercyful Fate.Enough happening in that song to fill 5 albums with stuff ->15 mins

Helloween,the Keeper of the keys saga.Around 15 minutes each

(Light of Day, Day of Darkness ) by green carnation is the album(song) you're looking for,although it's 5 minutes longer than you're limit .
http://www.metal-archives.com/release.php?id=445
this album is kind of rock(ish), if you want something heavier check out (crimson) by Edge of Sanity
http://www.metal-archives.com/release.php?id=474

Maybe Renaissance: http://www.metal-archives.com/release.php?id=86799

The Allman Brothers Band's Live At Fillmore East album is a must.

Iced Earth - Dante's Inferno (Power/Thrash Metal)
King Crimson - The Court Of The Crimson King (Prog Rock)
King Crimson - Moonchild (Prog Rock)
Lost Horizon - Highlander (The One) (Power Metal)
The Stone Roses - I Am The Ressurection (Alternative Rock is all I could describe it as)
The Stone Roses - Fools Gold (Alternative Rock)
Dream Theater - Metropolis Part 1 (Prog Metal)
Symphony X - The Odyssey (Prog Metal)
Seconding Mercyful Fate - Satan's Fall (Heavy Metal)

This.

Apart from that, you can never go wrong with prog rock. King Crimson and Yes are the most obvious choices if you're coming from a metal perspective, since they're quite riff-based. I especially recommend Fragile and Close to the Edge by Yes. I also just love Frank Zappa, but that might be much too far away from rock and too far into jazz.

For some more obscure prog rock, check out Grobschnitt. They're a Krautrock band from the seventies who are well-known for a song called Solar Music that could stretch out well beyond an hour in live performances. There's a small part of it on Youtube (http://www.youtube.com/watch?v=0P4ndS-6 ... re=related), but that only gives a glimpse of it. Unfortunately, the Solar Music Live album is very hard to get.

In case you like black metal, Bergthron fit the bill. They have tons of ideas packed into their songs, and they are generally quite long. Stay away from their recent stuff though, that's very different in style.

seconded, this for sure a must, in memory of elizabeth reed, and mountain jam are incredible

Mountain Jam is incredible, yes, but it's on Eat A Peach.

I second this! Flippin' great & amazing album that is!!

Try Why Angels Fall debut, The Unveiling. Two songs ranging from 34 to 44 minutes of doom/death with progressive, ambient, liturgical and other influences. Quite varied to say the least. (And don't trust my shitty description to do it any justice)