Okay, here's my list of "obscure forgotten classics" in prog metal - I might be forgetting some right now, but this is a quick run down of the more important ones in my collection:
Australia:
Vauxdvhil (their "To Dimension Logic" is a progressive album in the true sense of the word - it doesn't sound like anyone else - epic PROG metal)
Austria:
Nothingfaith ("Sigiriya" is one of those obscure albums not many have heard of. It's a quirky kind of prog metal that takes parts from both the Fates Warning (Arch-era), Mekong Delta (the classic/orchestral parts) and Dream Theater (the prog metal flow) - loves it!)
Denmark:
Behind The Curtain (imagine Psychotic Waltz teaming up with Symphony X to create a Dream Theater styled album)
Carisma (a band who didn't know what they were doing - the guys in the band never viewed this as a metal or prog album at all, but it's a fantastic concept album that should appeal to all who likes great melodies)
Chrome Shift (Dream Theater light with some clear hard rock melodies - wonderful album)
Eidetic (if you can find the demo's you're in for a real treat. Totally obscure Danish band creating music somewhere between Fates Warning and Alice In Chains)
France:
Manigance (someone already mentioned this, so I'll just add that you NEED to try it, even if the lyrics are in French)
Germany:
Deathrow ("Deception Ignored" is a classic thrash meets prog metal album - might be an aquired taste)
Depressive Age (East German goth meets power meets prog metal - imagine Type O Negative doing prog

)
End Amen (side project with people from Deathrow and Psychotic Waltz - very original but also not an easy album to "get into")
Koyaanisqatsi (soundscore prog metal - instrumental stuff - one of the most fantastic albums that never got released)
Life's Artist (the entire band - except the vocalist - later on became the backing band for Buddy Lackey's first solo album - thrashy prog/power with a unique songwriting approach. I know a lot of people hate this disc - I love it)
Mekong Delta (CLASSIC!!! 'nuff said)
Payne's Gray (mentioned above by someone else - check it out, crazy mix of prog, power, jazz and whatever else can be thrown together)
Sunblaze ("Illuminating Heights" is a true classic mini/EP - prog metal with big orchestrations)
Greece:
Breaking Silence (Fates Warning styled prog metal)
Holland:
Elegy (perhaps not "obscure" but their first 2 discs are some of my favorite melodic prog metal albums ever)
Israel:
Mercenary (another of those albums that never got released - what a shame - with a good production and a proper release this could have gone far. Good to see Eden (the keyboardist) later on show up on Orphaned Land)
Italy:
Madsword (Dream Theater styled prog metal)
Time Machine ("Act II Galileo" will always remain as one of my favorite CDs. Epic prog metal with a ton of wonderful melodies)
Norway:
Manitou (Fates Warning worship!!! Oyvind (later in Spiral Architect) is a brilliant vocalist)
Trivial Act (Dream Theater meets Fates Warning - great stuff)
Sweden:
Abstract Algebra (progressive doom metal with Mats Leven delivering one of the best vocal performances on any album ever!)
Elsesphere (another little gem - I worked really hard on making these guys a success, but a horrible label situation just took the fun out of it for all of us - that said, this album ROCKS!)
Hexenhaus (thrashy prog with a hint of doom here and there)
Mayadome (classic Dream Theater style, done better than on most DT albums)
Veni Domine (progressive doom metal! Candlemass meets Queensryche and Fates Warning)
UK:
Quest, the (Queensryche style prog)
Siam (melodic prog metal with a bit of Queensryche style here and there, but also a good deal of hard rock influences. Tony Mills is a fantastic vocalist)
USA:
Arch, John (ex-Fates Warning vocalist delivers a great prog metal EP ... I want more than just these 2 songs ... please?)
Black Symphony, the (first 2 albums are CLASSICS!!! Ask Glenn for a description and he'll be here all day

)
Catharsis (Fates Warning meets Psychotic Waltz style!)
Damn The Machine (heavy metal with a proggy edge - the Poland brothers are awesome
Digital Ruin (Q-ryche meets Fates Warning - good melodies, but not so good production)
Eternity X ("The Edge" is one of my ultimate favorite CDs!!! This is THE album to get)
Heir Apparent ("One Small Voice" is a classic for Q-ryche fans)
Hittman (the debut was pure Q-ryche worship, whereas the 2nd album "Vivas Machina" managed to blend in Bon Jovi style hard rock and in my opinion succeeded to create a brilliant disc)
Ice Age (someone already mentioned them - "Liberation" is a great great disc)
Last Things, the (This is some obscure stuff!!! Crazy / weird prog metal with strange percussions, bagpipes and whatnot)
Lord Bane (duh!!! See post above)
Mystic Force (Keith Menser and his band were fantastic - classic US prog / power metal)
Quiet Room, the (these guys came out of nowhere and took me by surprise first time I heard their demos. I actually worked together with Nordic Metal then trying to get them signed, but in the end they signed with another label. "Introspect" is a fantastic DT styled prog metal album and eventhough a lot of fans hate their second disc, I actually really liked that one too)
Sacred Warrior (Christian band playing some of the best Q-ryche styled prog ever)
Seventhsign (Fates Warning copy cat? Well perhaps so, but Gregg Analla sure can sing!)
Titan Force (Harry Conklin's "other band" - this doesn't remind of Jag Panzer except for his voice - this is way closer to prog than power - both "Titan Force" and "Winner/Loser" are classics!)
As mentioned above, there's a lot of bands I have forgotten here, but these were the ones that came to mind first, so give some of them a shot ...
c.