Step aside, amateurs...
I'm just listing progressive shit, because I can't stand most 80s/early 90s metal/hair bands (aside from Tesla and Maiden, of course).
Dominici (Dream Theater's original vocalist)
Dead Soul Tribe
Kayo Dot (might be a bit left-field for most as it combines elements of jazz, classical, and metal)
Maudlin of the Well (Toby from Kayo Dot's first, and better, band)
Redemption (they seem to like the shit out of Dream Theater as their music and vocals are quite a bit alike)
OSI (featuring Jim Mattheos, guitarist of Fates Warning who, strangely enough, I've not listened to and Kevin Moore, who is the old keyboardist of Dream Theater. Mike Portnoy of Dream Theater played drums on the first two releases, but Gavin Harrison of Porcupine Tree is playing drums on their next release, which comes out next month)
Liquid Tension Experiment (Portnoy, Petrucci, and Rudess from Dream Theater)
Pain of Salvation
This stuff is progressive, but has shouted/growled vocals. Not too sure if you're into that sorta thing, but whatever...
Intronaut (Danny Walker is an excellent, excellent drummer!)
Baroness (The dual guitar attack of The Red Album made album of the year for me in 2006)
Dillinger Escape Plan (their earlier stuff was pretty harsh, but their newer stuff contains some pop elements that make it a bit easier to listen to)
Opeth (If anything else, listen to the Damnation album -- it's the antithesis of heavy -- very 70s progesque)
Mastodon (they have gotten progressively mellower with each release, and their newest release, which is out next Tuesday, is really laid back from anything else they've ever done)