Are many people familiar with Agalloch? If not, be sure to check out their 15 minute epic masterpiece 'In the Shadow of Our Pale Companion, it is essential listening for prog metal fans.
Yup, I've got that album.
If you're into that spacey sorta metal, it's called Post-Metal, I can recommend some bands and albums for you.
maudlin of the Well - get Bath or Leaving Your Body Map
Kayo Dot - Choirs of the Eye
Amesoeurs - self-titled
Wolves in the Throne Room - Two Hunters
Pelican - The Fire In Our Throats Will Beckon the Thaw
Isis - Panopticon
Neurosis - Through Silver in Blood
Intronaut (as mentioned before
) - Prehistoricisms
Yakuza - Transmutations
As for more regular prog-metal:
Animals as Leaders
Blut aus Nord
Cobalt
The Dillinger Escape Plan
Disillusion
Dredg (more prog-rock)
Edge of Sanity
Enslaved
Fair to Midland
Fellsilent (if you're into Meshuggah-ish sorta stuff)
Fredrik Thordendal's Special Defects (same again)
Gordian Knot
Gorguts
Green Carnation
Misery Signals (their newest album especially)
Negura Bunget
Ne Obliviscaris (awesome Australian Prog. BM band)
Obscura (tech. death, but huge prog influences)
The Ocean
Pain of Salvation
Periphery (Meshuggah-ish)
Riverside
Sikth
Sleepytime Gorilla Museum
Strapping Young Lad (anything to do with Devin Townsend, really)
TesseracT (Meshuggah-ish)
Textures (Meshuggah-ish again)
Unexpect
Vanden Plas
Watchtower
+ other awesome bands already listed, i.e. Cynic, Gojira etc.
I would've listed more, but I think that's enough.
Should get you started
For more info on the bands go to
www.progarchives.com. It's one of my main resources to finding new music, specific categories updated regularly.